FibroScan vs Ultrasound for Fatty Liver: Which Test Do You Need?

Your GP says you may have fatty liver. Next, someone mentions a scan. But which one? An ultrasound? A FibroScan? Both?

It's a fair question. Both tests use sound waves. Both are quick and painless. However, they answer different questions. An ultrasound shows you a picture of your liver. A FibroScan gives you two numbers: how much fat is in your liver, and how stiff it is.

That difference matters. In fact, it can change what happens next for you. This guide explains what each test shows, how accurate each one is, what NICE says, and how to choose.

Key Takeaways

An ultrasound takes a picture of your liver. It can show fat, gallstones, lumps and signs of severe damage.
A FibroScan does not take a picture. It measures fat (the CAP score) and stiffness (a sign of scar tissue).
An ultrasound can miss mild fatty liver. It also can't measure early or moderate scar tissue.
A FibroScan can't find lumps, cysts or gallstones.
So many people need both. They work as a team, not as rivals.

The Short Answer

Here's the simple version.

Want to know if you have fat in your liver, or if there is another cause for your symptoms? An ultrasound is a good first look.
Want to know if that fat has started to scar your liver? You need a test like a FibroScan.

Why does scar tissue matter so much? Because it is the part that tells doctors how serious fatty liver is. Fat on its own often does no harm. Scar tissue is what can lead to cirrhosis over time. You can read more in our guide to fatty liver disease (MASLD).

What Is a Liver Ultrasound?

An ultrasound is the scan many people know from pregnancy. A trained person moves a small probe over your tummy. Sound waves bounce off your organs. A computer turns the echoes into a live picture.

It is safe, uses no radiation and does not hurt. A liver scan takes about 10 to 20 minutes, says Liver UK, the UK liver charity once known as the British Liver Trust.

What an Ultrasound Can Show

Fat in the liver. Fat makes the liver look brighter than normal on the screen. Doctors call this a "bright" or "echogenic" liver.
Other causes of your symptoms, such as gallstones, cysts, lumps or a blocked bile duct.
The size and shape of your liver.
Signs of severe scar tissue (cirrhosis), such as a lumpy edge or a large spleen.

That's why the NHS often uses ultrasound when your blood tests show a liver problem. It helps rule out other causes, too (NHS).

What an Ultrasound Can't Show

An ultrasound has two big blind spots.

First, it can miss mild fat. It works best once a fair amount of fat has built up. One review found standard ultrasound is less reliable when fat affects under about 30% of the liver (Yilmaz and Kaya, 2023).

Second, it cannot measure scar tissue, unless the damage is already severe. A liver with moderate scars can look normal. As Cambridge University Hospitals puts it, a standard ultrasound "does not, however, assess scarring, and hence you may require both a FibroScan and an ultrasound" (CUH).

What Does "Grade 1, 2 or 3 Fatty Liver" Mean?

You may see a grade on your ultrasound report. Grade 1 is mild. Grade 2 is moderate. Grade 3 is severe.

These grades describe how bright your liver looks. They are based on what the person who does the scan sees, so two people may grade the same liver a little differently.

Most important of all, the grade is about fat, not scars. A grade 3 liver may have no scar tissue. A grade 1 liver may have some. So the grade alone can't tell you how healthy your liver is. If you want to know what your grade means for recovery, see how long it takes to reverse fatty liver.

What Is a FibroScan?

A FibroScan is a special type of ultrasound test. Its medical name is transient elastography, or VCTE. "Elastography" just means a test of how stiff or springy a tissue is.

You lie on your back. A small probe rests on your skin over your liver, between your lower ribs. You may feel a light flick each time it takes a measure. It does not hurt. The whole scan takes about 5 to 15 minutes, and the numbers appear straight away (Liver UK).

Unlike a normal ultrasound, a FibroScan does not make a picture. Instead, it gives you two numbers.

Told You Have Fatty Liver But Not Sure How Serious It Is?

An ultrasound shows fat. It can't tell you if scar tissue has started.
A Fibrosis Scan checks fat and stiffness in one short visit.
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Liver Stiffness (kPa): A Sign of Scar Tissue

A healthy liver is soft. Scar tissue makes it stiff. The FibroScan sends a small wave through your liver and times how fast it travels. The stiffer the liver, the faster the wave. The result is shown in kilopascals (kPa), a unit of pressure.

A higher number usually means more scar tissue. However, there's no single "normal" number for everyone. The cut-offs depend on the cause of your liver problem. So a doctor should always read your result with your other tests (Liver UK). To see how scar tissue is graded from F0 to F4, read our guide to the fibrosis scan.

CAP Score (dB/m): A Measure of Fat

Most FibroScan machines also give a CAP score. CAP stands for controlled attenuation parameter. Put simply, it measures how much the sound wave fades as it passes through your liver. Fat makes it fade more. The result is shown in decibels per metre (dB/m). A higher score means more fat.

Because CAP is a number, it is easier to compare from one scan to the next. That makes it handy to track your progress.

What a FibroScan Can't Do

It can't find gallstones, cysts or lumps.
It can't show the shape of your liver or your spleen.
It can't diagnose a liver condition on its own. You still need blood tests, and often an ultrasound, too.

FibroScan vs Ultrasound: Side-by-Side

	Liver ultrasound	FibroScan
What you get	A live picture of your liver and nearby organs	Two numbers: stiffness (kPa) and fat (CAP, dB/m)
Finds fat?	Yes, but can miss mild fat	Yes, and it can pick up milder fat
Measures scar tissue?	No, only shows severe damage	Yes, gives an estimate
Finds gallstones, cysts or lumps?	Yes	No
How fat is reported	A grade (1 to 3) based on how bright the liver looks	A number you can track over time
Time	About 10 to 20 minutes	About 5 to 15 minutes
Food before the test	You may need to fast for up to 6 hours	You will usually fast for about 3 hours
Pain or radiation	None	None
Best for	A first look, and to rule out other causes	A check on whether fat has caused scar tissue

Times without food vary, so always follow the instructions from your clinic.

Which Test Is More Accurate?

It depends on what you want to measure.

For Fat in the Liver

A FibroScan's CAP score tends to pick up fat better, especially mild fat. In a review of nine studies, CAP correctly found mild fat in 87% of people who had it (Pu and others, 2019). Ultrasound is good at finding moderate or severe fat. However, it can miss the early stage, and the grade is partly a matter of opinion.

For Scar Tissue (Fibrosis)

Here, FibroScan is the clear winner. A standard ultrasound can't measure scar tissue at all until it is severe. A FibroScan can give an estimate from the early stages. It is best at telling apart a healthy liver from one with a lot of scar tissue. In fact, this is the main reason doctors use it.

Not Sure Which Liver Test Is Right for You?

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What Can Affect a FibroScan Result?

No test is perfect. A FibroScan result can come out higher than it should if:

you ate in the last few hours
your liver is inflamed right now, for example from a recent infection or a lot of alcohol
you have a blocked bile duct or heart failure

It can also be harder to get a clear result if you carry a lot of weight around your middle. A larger probe often helps with this (Yilmaz and Kaya, 2023). That's why your result should be read by someone who knows your full history.

What Does NICE Say?

NICE writes the health guidance used across the NHS in England. Here's what it says about these tests.

Blood tests alone are not enough. NICE says routine liver blood tests should not be used to rule out fatty liver (NICE NG49).
Ultrasound is the test for children. NICE advises a liver ultrasound to check children and young people at risk.
Scar tissue needs its own test. NICE says everyone with fatty liver should be offered a check for advanced scar tissue. It suggests a blood test called the ELF test (NICE NG49).
FibroScan is used to check for cirrhosis in some groups. These include people with fatty liver and advanced scar tissue, and people with alcohol-related liver disease (NICE NG50).
FibroScan can be offered outside hospital. NICE supports its use in community settings, as long as clear local plans are in place (NICE HTG682).

Note what is not on this list. NICE does not use ultrasound to judge scar tissue in adults. So a "normal" or "fatty" ultrasound report is not the end of the story.

Can You Have Both Tests?

Yes. In fact, for many people, that's the best plan.

Think of it this way. The ultrasound looks at the outside of the problem. Is there fat? Are there other problems, like gallstones? The FibroScan looks at the impact. Has the fat started to scar the liver?

A common path looks like this:

1. Blood tests show a liver problem, or an ultrasound shows fat by chance.
2. Your doctor checks your risk of scar tissue, often with a blood score such as FIB-4.
3. If that risk is not low, you have a FibroScan or ELF test.

At House of Health, you can have a liver and gallbladder ultrasound and a Fibrosis Scan at our clinic in Birmingham. A consultant can then look at both results together.

Which One Should You Choose?

The right test depends on your question. Here's a rough guide. Your doctor will help you decide.

An Ultrasound May Suit You If

you have pain in your upper right tummy
your doctor wants to rule out gallstones, cysts or lumps
you have never had a scan of your liver before
your blood tests are abnormal and the cause is not clear

A FibroScan May Suit You If

you already know you have fatty liver
you have type 2 diabetes or carry extra weight, which raise your risk of scar tissue
you drink more than the advised limit of 14 units a week
your FIB-4 or other blood score is not low
you want a number you can track as you lose weight or change your habits

If your ultrasound says "fatty liver" and no more, a FibroScan is often the logical next step. It tells you whether that fat has done any harm.

How to Get Ready for Each Test

Ultrasound: you may be asked not to eat for up to 6 hours. Water is usually fine (Liver UK).
FibroScan: you will usually be asked not to eat for about 3 hours. Clear drinks are fine, but skip fizzy drinks (Liver UK).
For both: wear loose clothes with a separate top. Keep up your usual medicines unless told otherwise.

When to See a Doctor

See a GP or a liver specialist if:

a scan or blood test shows a liver problem
you have risk factors such as type 2 diabetes, extra weight or a lot of alcohol
you feel tired all the time or have a dull ache under your right ribs

Get help fast, from your GP or NHS 111, if your skin or the whites of your eyes turn yellow, or your tummy or legs swell. If you have cirrhosis, call 999 if you vomit blood or your poo is black (NHS).

Frequently Asked Questions

Is a FibroScan better than an ultrasound?

Not better, just different. A FibroScan is better to check for scar tissue and mild fat. An ultrasound is better to see the shape of your liver and to find gallstones or lumps. Many people need both.

Can an ultrasound detect fatty liver?

Yes. Fat makes the liver look brighter. However, an ultrasound can miss mild fatty liver, and it can't tell you if the fat has caused scar tissue.

Is a FibroScan the same as a liver ultrasound?

No. A FibroScan uses ultrasound, but it does not make a picture. It measures how stiff your liver is and how much fat it holds.

Can a FibroScan replace a liver biopsy?

Often, yes. For many people, a FibroScan and blood tests give enough information, so they don't need a biopsy. However, a biopsy may still help if the results are unclear.

What is a normal CAP score?

There is no single cut-off that fits everyone. A higher CAP score means more fat. Ask the person who reads your scan to explain your number in the context of your health.

Does ultrasound elastography do the same job as a FibroScan?

Some ultrasound machines can measure stiffness too. This is called shear wave elastography. It works in a similar way, but the numbers are not the same as FibroScan numbers. So if you want to track change over time, stick with the same type of test.