AST · low result
Low AST levels: what they mean (and why it is usually nothing)
Short answer
A low AST — below the lab's lower limit, often under 8–10 U/L — is almost never a medical problem. AST is an enzyme released from liver, muscle and other cells; a low level means little is being released, which is normal in many healthy people and more common in women, older adults, and people with low muscle mass or small body size. Vitamin B6 (pyridoxine) deficiency lowers the measured activity because B6 is the enzyme's cofactor — seen with alcohol use, malnutrition, isoniazid and hemodialysis — and chronic kidney disease lowers AST independently. It does not indicate liver damage and has no treatment; as with a low ALT, in frail older adults it tracks with low muscle mass, which is the thing worth addressing.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- A low AST needs no urgent action on its own. Seek care for symptoms, not the number — unexplained weight loss, progressive weakness, or jaundice (which would come with other abnormal liver values).
What is the normal range for AST?
- Male, age 18+: 8.00 – 48.0 U/L
- Female, age 18+: 8.00 – 43.0 U/L
Full reference table, citations and testing options: AST biomarker page.
What are the common causes of low AST?
- Normal variation — many healthy adults have an AST of 8–15 U/L; the lower limit is a statistical boundary
- Female sex, older age, low body and muscle mass, frailty
- Vitamin B6 (pyridoxine) deficiency — alcohol use disorder, malnutrition, isoniazid, dialysis; the assay measures activity, which depends on B6
- Chronic kidney disease and hemodialysis — AST runs low enough that liver disease can hide behind a 'normal' value
- Pregnancy — reference ranges run slightly lower
- Low-protein diets and malnutrition
- Laboratory method — assays that do not add pyridoxal phosphate read lower in B6-deficient people
What symptoms go with low AST?
- None — a low AST itself causes no symptoms
- Any symptoms belong to a cause: cracked lips, a sore tongue, tingling or anemia with B6 deficiency; weakness and muscle loss with frailty; the features of kidney disease
What do clinicians usually check next?
- If you feel well and the rest of the liver panel is normal, nothing further is needed
- Check ALT, alkaline phosphatase, bilirubin and albumin on the same panel — a low AST with the rest normal is not a liver finding
- Consider a vitamin B6 level when there is alcohol use, dialysis, isoniazid treatment, poor nutrition or unexplained neuropathy
- Kidney function (creatinine, eGFR), since CKD lowers AST and changes how liver tests are read
- In older adults, think about nutrition and muscle — protein intake and resistance exercise
- Do not repeat the test for the low AST itself
Follow-up tests available at TestWell: ALT Test (Alanine Aminotransferase) ($16.99), Vitamin B6 Test (Pyridoxine) ($50.99).
How do you recheck AST?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Liver Health Panel | Panel · 4 tests | $59.99 | No | 2–5 business days |
| Fatty Liver Panel | Panel · 6 tests | $92.99 | Yes | 2–4 business days |
| Post-COVID Recovery Panel | Panel · 7 tests | $99.99 | Yes | 2–4 business days |
| Liver Function Panel | Test · 7 biomarkers | $19.49 | No | 1–3 business days |
Common questions
Is a low AST bad?
No. A low AST means little enzyme is leaking from liver and muscle cells, which is the healthy direction. It is common in women, older adults and smaller people and is not a sign of disease.
What does an AST of 8 mean?
A normal liver and muscles that are not releasing much enzyme. In an otherwise healthy person it needs no follow-up. In someone frail, on dialysis, drinking heavily or malnourished it can reflect low muscle mass or vitamin B6 deficiency, which are worth looking at for their own sake.
Can a low AST mean liver damage?
Almost never — injured liver cells release more AST, not less. In advanced cirrhosis so little working tissue remains that AST can be normal or low, but then albumin, bilirubin, platelets and the clinical picture are clearly abnormal and the AST is not the clue.
Why would B6 deficiency lower AST?
AST (like ALT) needs pyridoxal phosphate, the active form of vitamin B6, to work, and the laboratory measures the enzyme's activity rather than its amount. In B6 deficiency the result reads low; replacing B6 brings it back up. Dialysis patients and heavy drinkers are the groups where this matters.
Low AST and low ALT together — what does that mean?
The same things: normal variation, low muscle mass, B6 deficiency or kidney disease. Both enzymes depend on B6 and both track muscle mass, so they usually move together. With a normal rest-of-panel, no action is needed.
Should I retest a low AST?
Not on its own. It will appear on the next routine metabolic or liver panel. Retest sooner only if there is a reason to look at liver, kidney or nutrition for other symptoms.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.