What is FIB-4?
FIB-4 (Fibrosis-4 index) is a calculation based on four values from a routine blood test:
- Age
- AST (a liver enzyme)
- ALT (another liver enzyme)
- Platelet count
The formula is: (Age × AST) / (Platelets × √ALT). Your GP doesn't do this by hand — most pathology software calculates it automatically when they request a liver function test.
FIB-4 reference ranges
| FIB-4 score | Meaning | Next step |
|---|---|---|
| < 1.3 (or < 2.0 if 65+) | Low risk of advanced fibrosis | Routine annual LFTs |
| 1.3 – 2.67 | Indeterminate — could be early fibrosis | Elastography to clarify |
| > 2.67 | High risk of advanced fibrosis | Specialist hepatology referral |
What happens to FIB-4 on GLP-1 medications?
Over the first 3–6 months of GLP-1 therapy, ALT and AST typically fall as liver fat reduces. This can lower a FIB-4 score over time. So a baseline FIB-4 before starting (or in the first couple of months) gives you a clean reference point.
A transient rise in liver enzymes early in treatment is not unusual. It usually settles. Persistent or symptomatic enzyme rises should be investigated.
Why indeterminate FIB-4 on GLP-1 patients should get elastography
The whole point of the indeterminate range (1.3–2.67) is that it's ambiguous. Some patients in this range have significant fibrosis; some don't. FIB-4 alone can't tell you which.
Elastography resolves this. It measures liver stiffness directly in kilopascals (kPa). A kPa above 8 in a MASLD patient typically indicates significant fibrosis worth monitoring; below 8 is reassuring.
For GLP-1 patients, this matters for two reasons. First, knowing your starting fibrosis stage helps you (and your GP) understand the stakes of treatment. Second, a baseline kPa gives you something to track — most responders show meaningful reductions at 12 months.
The referral pathway: from your GP to an elastography clinic
- Your GP orders a liver function test and notes the FIB-4 result
- If indeterminate, your GP refers you for elastography
- You attend a participating clinic — 10–15 minute appointment, no needles
- Your kPa result goes back to your GP within days
- Your GP decides whether to refer to a specialist or manage in primary care
Frequently asked questions
What does an indeterminate FIB-4 mean if I'm on Ozempic?
An indeterminate FIB-4 (1.3–2.67) means your liver enzyme and platelet pattern doesn't clearly rule out fibrosis. The next step is elastography to measure actual liver stiffness, which gives you and your GP a precise stiffness number to act on.
Will Ozempic change my FIB-4 score over time?
Yes. As liver fat reduces, ALT and AST typically fall, which can lower FIB-4. A baseline FIB-4 at the start of treatment gives you a reference point so you and your GP can see the improvement at 6 and 12 months.
Do I need elastography if my FIB-4 is normal on a GLP-1?
Usually not. A FIB-4 below 1.3 (or below 2.0 if you're 65+) has a 95–97% negative predictive value for advanced fibrosis. Routine annual LFTs are sufficient unless something changes.
How accurate is FIB-4 for GLP-1 patients?
FIB-4 is well-validated as a screening tool. It's not perfect — about 30–40% of patients fall in the indeterminate range — but elastography handles the indeterminate cases efficiently.
Indeterminate FIB-4? Get elastography near you
A baseline kPa measurement clarifies whether you have significant fibrosis and gives you a reference point to track over 12 months on GLP-1 therapy.
This page is educational and not medical advice. Always discuss your GLP-1 treatment and liver monitoring with your GP.