- Liver Enzyme Interpretation and Liver Function Tests
- Case 2
- Interpreting Liver Enzyme Elevations
- LIVER FUNCTION TESTING
- Serum Bile Acids
- Alanine Aminotransferase (ALT)
- ALT Blood Test (SGPT) for Liver – HealthLabs.com
- How Does an ALT Test Work?
- Why take an ALT Test?
- Signs of Liver Damage or Failure
- What can cause ALT levels to rise?
- Things to Know Beforehand
- How Is the Test Taken?
- What your ALT Test Results mean
- What is Alanine Aminotransferase (ALT)? Test & Normal Range
- ALT Blood Test
- Normal Range
- Low ALT
- High ALT
- Upper Limits of Normal for Alanine Aminotransferase Activity in the United States Population
- What Is an Alanine Aminotransferase (ALT) Test?
- Blood Test: Alanine Aminotransferase (ALT, or SGPT)
- What Is an ALT Test?
- Why Are ALT Tests Done?
- How Should We Prepare for an ALT Test?
- How Is an ALT Test Done?
- Can I Stay With My Child During an ALT Test?
- How Long Does an ALT Test Take?
- What Happens After an ALT Test?
- When Are ALT Test Results Ready?
- Are There Any Risks From ALT Tests?
- Alanine aminotransferase (ALT) test: Uses and results
Liver Enzyme Interpretation and Liver Function Tests
Brigitte B. McAtee, DVM
Jonathan A. Lidbury, BVMS, MRCVS, PhD, DACVIM, DECVIM-CA
Texas A&M University
Hepatobiliary disease is an important cause of morbidity and mortality in dogs and cats and can present a diagnostic challenge for two main reasons. First, patient signalment varies because liver disease and dysfunction can occur in cats and dogs of any age, sex, or breed (see Case Studies).
Despite this, the patient’s signalment can sometimes give important clues because certain breeds have disease predispositions; for example, Labrador retrievers are predisposed to copper-associated chronic hepatitis.
Second, elevations of serum liver enzyme activities are commonly encountered in small animal practice but are not specific for primary liver disease. However, early in the course of liver diseases, such as chronic hepatitis, patients may have no or only subtle, nonspecific clinical signs, such as intermittent anorexia or lethargy.
In these patients, increased liver enzyme activities may be the first indicator of a problem. More liver-specific clinical signs, such as icterus, ascites, edema, polyuria/polydipsia, and hepatic encephalopathy, tend to occur late in the course of disease, when it is often too late to prevent its progression.
Therefore, early diagnosis of liver disease often relies on serum biochemical testing, which may prompt further diagnostics, including liver function testing. This article reviews the interpretation and limitations of serum liver enzyme activity and liver function tests.
Signalment and Presentation
A 3-month-old female intact Irish wolfhound presents for stunted growth and episodes of intermittent lethargy and disorientation.
Results of Diagnostic Testing
A serum biochemistry panel is performed, with the results in Table A. The fasted ammonia concentration is 175 mcg/dL (normal range, 0–50 mcg/dL). Preprandial and postprandial (2-hour) SBA are 40 mcmol/L (normal, 0–8 mcmol/L) and 102 mcmol/L (normal, 0–30 mcmol/L), respectively.
The combination of hypoalbuminemia, decreased BUN, and hypocholesterolemia suggests decreased hepatic synthetic capacity. The ALT and AST activities are within normal limits, making hepatocellular damage unly; the ALP activity is only mildly elevated, probably because the dog is growing.
The ammonia concentration and SBA results suggest portosystemic shunting and/or hepatic insufficiency.
Given the patient’s signalment, clinical findings, and laboratory abnormalities, a congenital portosystemic shunt is ly and imaging (ultrasonography and/or computed tomography) is warranted.
Signalment and Presentation
An 8-year-old male neutered Labrador retriever presents for a 3-month history of decreased appetite and weight loss.
Results of Diagnostic Testing
A serum biochemistry panel is performed, with the results in Table B. The fasted ammonia concentration is 150 U/L.6 Bone ALP may also be elevated in patients with osteomyelitis or osteosarcoma.
Dogs with hyperadrenocorticism and those receiving glucocorticoids can be expected to have increased ALP activity due to the glucocorticoid-induced isoenzyme.
Conditions that can cause an increase in ALP activity include those listed in Table 1.
The highest activities of ALP have been reported with conditions such as cholestasis, steroid hepatopathy, chronic hepatitis, and hepatic necrosis.7 This lack of tissue specificity can make increases in activity of ALP hard to interpret.
The half-life of ALP is approximately 70 hours in dogs and 6 hours in cats.
3 In cats, which lack the glucocorticoid-induced isoenzyme with a shorter half-life, increases of serum ALP activity are more specific for hepatobiliary disease than in dogs and are generally clinically relevant.
GGT is associated with the cell membranes of hepatocytes that form the bile canaliculi and bile ducts, as well as periportal hepatocytes. It is a marker of intrahepatic (eg, feline hepatic lipidosis) or extrahepatic (eg, bile duct obstruction) cholestasis. In dogs, it has a higher specificity (87%) and lower sensitivity (50%) for hepatobiliary disease compared with ALP.
7 In general, GGT is a more sensitive marker of feline hepatobiliary disease than ALP. However, in cats with feline hepatic lipidosis, GGT is generally only mildly elevated.8 No definitive studies determining the half-life of GGT have been performed in cats or dogs.
However, serum GGT and ALP activities decrease after liver injury at a similar rate in dogs, suggesting that they have a similar half-life.9
Interpreting Liver Enzyme Elevations
The degree of the increase in hepatocellular-damage enzyme activities may help stratify disease severity as follows5:
- Mild: 2- to 3-fold elevation in activity
- Moderate: 5- to 10-fold elevation in activity
- Marked: >10-fold elevation
However, such increases do not always correlate with severity of disease. This is true in dogs and cats with portosystemic shunting and dogs with end-stage chronic hepatitis, in which hepatocytes are replaced by fibrous tissue. Therefore, the degree of liver enzyme increase should be interpreted with caution.
Because the liver has a large regenerative capacity, the degree of liver enzyme elevation should also not be used to indicate prognosis.
For example, a dog with acute liver injury may have severely increased serum ALT activity but can still make a full recovery.
Longitudinal monitoring trends in liver enzyme activities can help in determining chronicity and monitoring disease progression and/or response to treatment.
In evaluating liver enzymes, it is important to determine what type of elevation pattern is present (ie, hepatocellular damage versus cholestasis).
A relatively greater increase in ALT and AST activity indicates hepatocellular damage, while a greater increase in ALP and GGT activity indicates cholestasis, which could be intrahepatic or extrahepatic.
Establishing the pattern may help narrow the differential diagnosis. However, some liver diseases can display a mixed pattern (eg, cholangitis, phenobarbital hepatopathy).
LIVER FUNCTION TESTING
Routine biochemical testing can give clinicians an insight into many liver functions.
Box 2 presents common abnormal results of biochemical tests that can have liver-related causes as well as important differential diagnoses to consider for these test results.
However, because of the liver’s functional reserve capacity, these tests are not sensitive for liver insufficiency. Abnormal results can also be caused by other conditions and thus also lack specificity.
It is important for clinicians to not only look for analytes that are flagged as being outside their respective reference intervals but also look at their actual values.
For example, serum albumin, cholesterol, and blood urea nitrogen (BUN) concentrations toward the lower limit of the reference interval suggest hepatic insufficiency or portosystemic shunting.
Monitoring trends in these values over time can also be informative.
Because of the limited sensitivity and specificity of biochemical tests, patients with confirmed or suspected liver disease sometimes require additional liver function testing to better characterize their disease.
Serum Bile Acids
Measurement of the total concentrations of serum bile acids (SBA) aids in the diagnosis of patients with portosystemic shunts and in the assessment of hepatic function. Potential indications for SBA measurement include:
- Suspicion for portosystemic shunting (eg, seizures, other signs of encephalopathy)
- Persistently increased liver enzyme activities, especially ALT
- Severe hypoalbuminemia (
Alanine Aminotransferase (ALT)
Sources Used in Current Review
2019 Review completed by H.L.Chong, MD, FRSPH, IPFPH, Clinical Scholar, Faculty of Public Health of the Royal Society of Physicians of United Kingdom.
ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. The American Journal of Gastroenterology. Volume 112. January 2017.
(Updated June 13, 2019) Sood, G MD. Acute Liver Failure Workup. Medscape Reference. Available online at https://emedicine.medscape.com/article/177354-workup#c2. Accessed August 2019.
McPherson RA, Matthew R, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia: Elsevier Saunders; 2011.
Sources Used in Previous Reviews
Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. St. Louis: Mosby; 1998.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006, Pp 604-606.
Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds, (2005) Harrison's Principles of Internal Medicine, 16th Edition, McGraw Hill, Pp 1811-1815.
Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006, Pp 40-42.
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC, Pp 270-271.
Carey, W (January 1, 2009) Approach to the Patient with Liver Disease: A Guide to Commonly Used Liver Tests, Cleveland Clinic. Available online at http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/hepatology/guide-to-common-liver-tests/. Accessed February 2010.
Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson RA and Pincus MR, eds. Philadelphia: 2007, Pp 268-269.
(2000) Dufour, DR et al. National Academy of Clinical Biochemistry Standards of Laboratory Practice: Laboratory Guidelines for Screening, Diagnosis and Monitoring of Hepatic Injury http://www.aacc.org/SiteCollectionDocuments/NACB/LMPG/hepatic/hepatic_combined.pdf#page=3. Accessed February 2010.
(March 15, 2005) Giboney, P. Mildly Elevated Liver Transaminases in the Asymptomatic Patient. Am Fam Physician 2005; 71:1105–10. Available online at http://www.aafp.org/afp/2005/0315/p1105.html. Accessed February 2010.
(Feb 22, 2009) MedlinePlus Medical Encyclopedia: ALT. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003473.htm. Accessed February 2010.
Alanine Aminotransferase (ALT) (GPT), Serum. Mayo Clinic. Available online at http://www.mayomedicallaboratories.com/test-info/hematology/catalog/Overview/8362. Accessed September 2013.
Orlewicz, M. S. (Update April 20, 2012.) Alanine Aminotransferase. Medscape. Available online at http://emedicine.medscape.com/article/2087247. Accessed September 2013.
Nyblom, H. et. al. (July 2004.) High AST/ALT Ratio May Indicated Advanced Alcoholic Liver Disease Rather Than Heavy Drinking. National Center for Biotechnology Information PubMed. Available online at http://www.ncbi.nlm.nih.gov/pubmed/15208167. Accessed September 2013.
2016 review performed by Alan F. Weir, PhD, DABCC, Instructor, Fox Valley Technical College.
ALT Blood Test (SGPT) for Liver – HealthLabs.com
ALT is an enzyme found in many parts of the body, but the liver contains the highest concentration.
This enzyme, formerly known by the name serum glutamic-pyruvic transaminase, or SGPT, is used by the body to break down food into energy. ALT levels normally remain fairly low, but rise when your liver is damaged.
Because of this, a high ALT level are usually a straightforward indication that there is something wrong with your liver.
How Does an ALT Test Work?
Alanine transaminase, also known as ALT or SGPT, is an enzyme made by the liver to metabolize proteins. ALT is released into the bloodstream when liver cells are damaged.
An ALT test measures the amount of ALT in the blood to assess if the liver is damaged.
The most common reason to take an ALT test is to detect liver injury and to screen for/or help diagnose liver disease, as it is considered to be one of the best methods to identify liver issues.
Why take an ALT Test?
ALT blood tests are often part of liver function testing. The main reason to take an ALT test is if you or your doctor identify signs of liver damage or failure. It can also be taken to monitor the progression of liver diseases or to evaluate the effectiveness of treatment.
Signs of Liver Damage or Failure
Onset symptoms of liver failure include:
- Loss of appetite
As you can see, the initial symptoms of liver failure are so broad that it can be difficult, if not impossible, to diagnose without testing.
The following are symptoms of liver failure that indicate the disease has progressed to the point of requiring immediate treatment or hospitalization:
- Jaundice (yellow skin)
- Bleeding easily
- Swollen abdomen
- Hepatic encephalopathy (mental disorientation/confusion)
What can cause ALT levels to rise?
There are many things may increase the ALT levels in the blood. Some of these include:
- Alcohol abuse
- Hepatitis – an inflammatory condition of the liver
- Cirrhosis – severe scarring and poor overall performance of the liver caused by high exposure to toxins alcohol or viral infection
- Death of liver tissue
- A tumor in the liver
- Poor blood flow to the liver
- Hemochromatosis – a disorder that causes iron build up
- Mononucleosis – an infection usually caused by the Epstein-Barr virus
- Pancreatitis – pancreas inflammation
Things to Know Beforehand
You should tell your doctor about any drugs you are taking, as some prescription and over-the-counter medications can affect ALT levels. Acetaminophen (Tylenol) is a notable example. Your doctor may tell you to avoid taking some medications for a period of time prior to taking the test. Otherwise, there are not any precautions necessary to taking the test.
How Is the Test Taken?
Testing with Healthlabs.com is simple, quick, and easy. After you have purchased an ALT test and traveled to the lab you selected using our lab finder, a lab technician will perform a simple blood test.
The technician inspects your arm for vein visibility first, chooses a spot to draw the blood, cleans the area with antiseptic, and wraps an elastic band around your upper arm in preparation for collection. The lab technician then carefully injects a sterile needle into the vein and draws blood.
The entire process, depending on how busy the lab is, should take about 5-10 minutes.
What your ALT Test Results mean
The normal value of an ALT test depends on gender:
~29 to 33 U/L (units per liter) for men and ~19 to 25 U/L for women.
ALT levels typically fall somewhere within the 7 to 55 U/L range. Certain factors age and gender can affect this range, but doctors should be able to recognize abnormal values regardless.
Both excessively high and low ALT levels are considered to be unhealthy, but higher-than-normal levels are the most ly to indicate liver damage.
What is Alanine Aminotransferase (ALT)? Test & Normal Range
Alanine aminotransferase (ALT) is an important marker of liver health. Keep reading to find out why this marker is often part of liver function tests – and when you should be concerned about your levels.
Alanine aminotransferase or ALT (also known as SGPT) is an enzyme your body needs to break down proteins into energy [1, 2].
Healthy liver cells store most of ALT, but small amounts are also found in the kidneys, heart, muscles, fat tissue, intestines, and pancreas .
Normally, blood ALT levels are low. However, when liver cells are damaged due to illness, injury, or medication, they release ALT, increasing its blood levels .
Therefore, ALT blood levels are a marker of liver health: low levels typically indicate a healthy liver, while high levels suggest liver damage .
Before we talk about the ALT blood test, let’s take a look at what ALT normally does in the body.
ALT helps turn L-alanine and alpha-ketoglutarate into glucose that can be used for energy (via pyruvate) and L-glutamate which can be eliminated as waste or used to build new proteins [6, 7, 8, 9].
ALT Blood Test
An ALT blood test may be ordered to [10, 11, 12, 13]:
- Assess liver health
- Investigate symptoms of liver disease, such as abnormally yellow skin or eyes (jaundice), or pain in the upper-right section of the abdomen
- Monitor progression of a liver disease
- Evaluate the effectiveness of a treatment for liver disease
- Determine if the liver is involved in or damaged by a health condition, such as diabetes or heart disease
Since ALT is an enzyme, its levels are typically determined by measuring its activity (the rate at which ALT transforms L-alanine and α-ketoglutarate into pyruvate and L-glutamate) .
ALT levels are often measured together with the liver enzyme aspartate transaminase (AST). The ratio of AST/ALT is also sometimes used as a marker of liver health.
While ALT levels can signal the presence of liver damage, they cannot determine the type of damage, such as scarring, infection, or inflammation .
ALT is measured in units per liter of blood or U/L.
The normal range is around 7-35 U/L in women and 7-40 U/L in men. There may be some lab-to-lab variability in ranges due to differences in equipment, techniques, and chemicals used.
ALT levels typically do not change much during pregnancy. They may slightly increase during the final trimester, but generally still remain below 40 U/L [16, 17, 18, 19].
Low ALT levels are expected and normal – they are just uncommon in the general population. This is because reference ranges are where 95% of a healthy population falls into, which means that there are 5% of the people who are healthy and not within the reference range!
There are some factors that can decrease ALT, but they are not common. These include:
- Vitamin B6 deficiency [20, 21]
- Smoking 
- Regular exercise 
- Oral contraceptives or hormone replacement therapy [22, 24]
- Chronic kidney disease [25, 26]
Find out more about low ALT levels and associated conditions here.
High ALT levels often signal a problem with the liver. However, a result that’s higher than normal, doesn’t necessarily mean that you have a health condition that needs treatment. Your doctor will interpret your ALT result, taking into account your medical history, symptoms, and other test results.
ALT can increase due to various underlying issues. Causes shown below are commonly associated with high ALT levels. Work with your doctor or another health care professional to get an accurate diagnosis. Aforementioned conditions include:
- Liver diseases, such as fatty liver, viral hepatitis, other infections that affect the liver (mononucleosis), or liver cancer [27, 28]
- Liver damage due to toxins such as lead, mercury, or pesticides [11, 29, 30]
- Liver damage due to prescription and over-the-counter drugs and supplements [11, 31, 32, 33]
- Alcohol abuse 
- Anorexia 
- Obesity [36, 34, 37]
- Gallstones and gallstone-induced inflammation of the pancreas (pancreatitis) [38, 39]
- Muscle damage due to strenuous exercise, injury, or muscle disease [40, 41, 42]
- Tissue damage due to surgery or burns [43, 44]
- Heart attack or heart failure [45, 31]
- Underactive thyroid gland (hypothyroidism) 
- Abnormal red blood cell destruction (hemolysis) [46, 47]
Read through this post to learn more about the causes of high ALT and what you can do to decrease high ALT levels.
While one elevated ALT test doesn’t necessarily mean that you have a health condition that needs treatment, several high ALT tests or a high ALT test in conjunction with symptoms of liver damage or disease are a reason for concern. Your doctor should work on finding the underlying cause and treatment options .
Tests of other liver enzymes such as AST, ALP, bilirubin, and GGT can help create a more complete picture of liver health .
ALT is an enzyme your body needs to turn proteins into energy. Most of it is stored in your liver.
Your levels will usually remain stable and relatively low if your liver is healthy, while liver damage causes ALT to leak into the bloodstream in higher amounts. Thus, doctors typically order ALT to check liver function.
However, various other conditions beyond liver health can also affect your levels. That’s why doctors will analyze ALT alongside other markers of liver health AST, ALP, bilirubin, and GGT.
Upper Limits of Normal for Alanine Aminotransferase Activity in the United States Population
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What Is an Alanine Aminotransferase (ALT) Test?
The alanine aminotransferase (ALT) test is a blood test that checks for liver damage. Your doctor can use this test to find out if a disease, drug, or injury has damaged your liver.
Your liver does a lot of important things for you:
- It makes a fluid called bile that helps your body digest food.
- It removes waste products and other toxins from your blood.
- It produces proteins and cholesterol.
Diseases such as hepatitis and cirrhosis can damage your liver and prevent it from doing its many jobs.
This enzyme is found mainly in your liver. Smaller amounts of ALT are in your kidneys and other organs, too.
Your body uses ALT to break down food into energy. Normally, ALT levels in the blood are low. If your liver is damaged, it will release more ALT into your blood and levels will rise. (ALT used to be called serum glutamic-pyruvic transaminase, or SGPT).
Doctors often give the ALT test along with other liver tests.
Your doctor might recommend ALT if you have symptoms of liver disease or damage, such as:
Here are some reasons you might get this test:
- You've been exposed to the hepatitis virus.
- You drink a lot of alcohol.
- You have a family history of liver disease.
- You take medicine that's known to cause liver damage.
The ALT test can be done as part of a blood panel during a regular exam. If you've already been diagnosed with liver disease, your doctor can use the ALT test to see how well your treatment is working.
You don't need any special preparation for the ALT test. Your doctor might ask you to stop eating or drinking a few hours before the test.
Tell your doctor what prescription drugs or supplements you take. Some medicines can affect the results of this test.
A nurse or lab tech will take a sample of your blood, usually from a vein in your arm. He will first tie a band around the upper part of your arm to make your vein fill with blood and swell up. Then he will clean the area with an antiseptic and place a needle into your vein. Your blood will collect into a vial or tube.
The blood test should take only a couple of minutes. After your blood is taken, the lab tech will remove the needle and band, then put a piece of gauze and a bandage over the spot the needle went in to stop the bleeding.
The ALT blood test is safe. Risks are usually minor, and can include:
- Slight pain when the needle is inserted
- Fainting or feeling dizzy
You should get your results in about a day. A normal ALT test result can range from 7 to 55 units per liter (U/L). Levels are normally higher in men.
Slightly high ALT levels may be caused by:
Moderately high ALT levels may be because of:
Very high ALT levels can be caused by:
ALT usually is done as part of a group of liver function tests called a liver panel.
This panel also includes an aspartate aminotransferase (AST) test. AST is another liver enzyme. As with ALT, the levels of AST in your blood rise if your liver is damaged.
Comparing ALT with AST levels gives your doctor more information about the health of your liver. The ALT-to-AST ratio can help your doctor figure out how severe the liver damage is and what might have caused it.
To find out what type of liver disease you have, your doctor might also test the levels of other enzymes and proteins found in your liver, including:
Talk to your doctor to make sure you understand all of your liver test results. Also find out how these results might affect your treatment.
American Association for Clinical Chemistry: “ALT.”
Mayo Clinic: “Liver Disease: Definition.” “Liver function tests.”
Medscape: “Alanine Aminotransferase.”
National Heart, Lung, and Blood Institute: “What To Expect With Blood Tests.”
Nemours Foundation: “Blood Test: Alanine Aminotransferase (ALT, or SGPT).”
University of Rochester Medical Center: “ALT.”
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Blood Test: Alanine Aminotransferase (ALT, or SGPT)
A blood test is when a sample of blood is taken from the body to be tested in a lab. Doctors order blood tests to check things such as the levels of glucose, hemoglobin, or white blood cells. This can help them detect problems a disease or medical condition. Sometimes, blood tests can help them see how well an organ (such as the liver or kidneys) is working.
What Is an ALT Test?
An ALT test measures the level of alanine aminotransferase, also called ALT or SGPT. ALT is one of the enzymes that help the liver convert food into energy. High levels of these enzymes can be a sign that the liver is injured or irritated, and the enzymes are leaking the liver cells.
Why Are ALT Tests Done?
An ALT test may be done if a child has signs of a possible problem with the liver, such as jaundice (yellowish skin or eyes), dark urine, nausea, vomiting, or belly pain. It also might be done if a child is on medicine that makes high liver enzyme levels more ly.
How Should We Prepare for an ALT Test?
Your child may be asked to stop eating and drinking for 8 to 12 hours before the ALT test. Tell your doctor about any medicines your child takes because some drugs might affect the test results.
Wearing a T-shirt or short-sleeved shirt for the test can make things easier for your child, and you also can bring along a toy or book as a distraction.
How Is an ALT Test Done?
Most blood tests take a small amount of blood from a vein. To do that, a health professional will:
- clean the skin
- put an elastic band (tourniquet) above the area to get the veins to swell with blood
- insert a needle into a vein (usually in the arm inside of the elbow or on the back of the hand)
- pull the blood sample into a vial or syringe
- take off the elastic band and remove the needle from the vein
In babies, blood draws are sometimes done as a “heel stick collection.” After cleaning the area, the health professional will prick your baby's heel with a tiny needle (or lancet) to collect a small sample of blood.
Collecting a sample of blood is only temporarily uncomfortable and can feel a quick pinprick.
Can I Stay With My Child During an ALT Test?
Parents usually can stay with their child during a blood test. Encourage your child to relax and stay still because tensing muscles can make it harder to draw blood. Your child might want to look away when the needle is inserted and the blood is collected. Help your child to relax by taking slow deep breaths or singing a favorite song.
How Long Does an ALT Test Take?
Most blood tests take just a few minutes. Occasionally, it can be hard to find a vein, so the health professional may need to try more than once.
What Happens After an ALT Test?
The health professional will remove the elastic band and the needle and cover the area with cotton or a bandage to stop the bleeding. Afterward, there may be some mild bruising, which should go away in a few days.
When Are ALT Test Results Ready?
Blood samples are processed by a machine, and it may take a few hours to a day for the results to be available. If the test results show signs of a problem, the doctor might order other tests to figure out what the problem is and how to treat it.
Are There Any Risks From ALT Tests?
An ALT test is a safe procedure with minimal risks. Some kids might feel faint or lightheaded from the test. A few kids and teens have a strong fear of needles. If your child is anxious, talk with the doctor before the test about ways to make the procedure easier.
A small bruise or mild soreness around the blood test site is common and can last for a few days. Get medical care for your child if the discomfort gets worse or lasts longer.
If you have questions about the ALT test, speak with your doctor or the health professional doing the blood draw.
Alanine aminotransferase (ALT) test: Uses and results
The liver makes several enzymes, including alanine aminotransferase, or ALT. These enzymes help break down proteins so that the body can digest them.
Besides helping the liver break down proteins, ALT helps the liver perform its basic functions. Some of these include:
- filtering toxins from the blood
- storing nutrients and iron
- producing bile, which aids digestion
Most ALT that the liver produces stays within the organ. However, when the liver is damaged or inflamed, it may release ALT into the bloodstream.
When this happens, the level of ALT in the blood rises. Therefore, doctors use an ALT blood test to screen for liver disease or damage. Learn more about the test in this article.
A doctor orders an ALT test to look for problems with liver function. Many people have this test as part of a comprehensive metabolic panel.
The comprehensive metabolic panel is a routine blood test that checks a person’s glucose level, kidney function, and liver function. It is often part of a routine checkup that gives a doctor insight into an individual’s overall health.
Other times, a doctor orders the ALT blood test as part of a series of blood tests called liver panels if they suspect that a person’s liver is damaged or diseased.
Doctors may order liver panels if a person has symptoms of liver disease or damage. Symptoms of liver problems include:
- yellowing of the eyes and skin (jaundice)
- pain in the upper right quadrant of the abdomen
- referred pain in the right shoulder
- easy bleeding or bruising
- intense itching
- pale stools
- swelling in legs or abdomen
These symptoms can indicate liver disease, injury, or another problem that may be affecting the liver.
Medical problems that can cause elevated ALT levels include:
Certain medications can also cause ALT levels in the blood to be high.
Often, these levels are elevated before symptoms of liver damage occur, making the test useful for people at risk of liver damage.
When a doctor can detect liver damage early, they may be better able to treat it and prevent further injury.
People at risk of liver damage or disease include:
- people with a family history of liver disease
- people who have diabetes
- people who are overweight
- people who consume a lot of alcoholic beverages
- people taking certain medications
Doctors routinely order liver panels to monitor diagnosed liver disease or injury. The results of these tests can show how well the treatment plan is working.
A person with a healthy liver will have an ALT level in the normal range. The normal range can vary from laboratory to laboratory.
According to the Mayo Clinic, the normal range for adult males is 7–55 units per liter. Females may have a lower upper limit normal than males.
Age can also affect results. A person should speak with their doctor about what their results mean.
If a person has results above the normal range, this may indicate liver damage.
Causes of elevated ALT levels include:
- the destruction of liver cells
- a lack of blood flow to the liver
- cirrhosis, or severe scarring of the liver
- hemochromatosis, or iron buildup
- mononucleosis, an infection usually caused by the Epstein-Barr virus
- a tumor in the liver
A person should discuss their results with their doctor, who can say if the numbers returned are within a normal range.
If a person’s results are too low or high, a doctor can help determine the appropriate course of treatment.
People with higher ALT levels often need additional tests to discover the underlying cause of the liver damage and treat it.
An ALT blood test helps determine if a person has liver damage. Uncovering the cause of the problem often requires further testing.
The normal range for results tends to vary among facilities, and a doctor can discuss what the results mean on an individual basis.
Once they know the underlying cause of the liver damage, symptoms and test results, the doctor will discuss appropriate treatment options.