Fatty Liver Disease (MASLD/NAFLD): Symptoms, Causes and Treatment

Fatty liver disease happens when excess fat builds up inside the liver. The condition is now increasingly called metabolic dysfunction-associated steatotic liver disease, or MASLD. Until recently, it was usually known as non-alcoholic fatty liver disease, or NAFLD.

Most people with MASLD do not feel unwell and may only discover it after a blood test or scan performed for another reason. For many, the condition remains at the stage of simple fat accumulation and does not cause serious liver damage. In some people, however, the liver becomes inflamed and develops scar tissue. Over time, advanced scarring can lead to cirrhosis and increase the risk of liver failure or liver cancer.

The important question is therefore not simply whether there is fat in the liver. It is whether the liver is becoming inflamed or scarred, and whether associated conditions such as type 2 diabetes, high blood pressure, excess weight and abnormal cholesterol are being controlled.

What is fatty liver disease, MASLD and NAFLD?

The liver normally contains a small amount of fat. Fatty liver disease is diagnosed when more fat than expected accumulates within liver cells.

The terminology has changed because the older name, non-alcoholic fatty liver disease, defined the condition mainly by what had supposedly not caused it. The newer name focuses instead on its close relationship with metabolic health.

MASLD stands for metabolic dysfunction-associated steatotic liver disease. The term generally describes fat in the liver occurring alongside at least one metabolic risk factor, such as:

• excess weight or an increased waist measurement;
• type 2 diabetes or raised blood sugar;
• high blood pressure;
• high triglycerides;
• low levels of protective HDL cholesterol.

You may still hear doctors use NAFLD because the old term remains in many clinical guidelines, computer systems, medical letters and research papers. In everyday practice, MASLD, NAFLD and metabolic fatty liver disease usually refer to substantially the same condition.

The wider umbrella term steatotic liver disease describes any condition involving excess fat in the liver. Fat can also accumulate because of alcohol, certain medicines, rapid weight loss, malnutrition and less common inherited or metabolic conditions.

The distinction matters because not every fatty liver is caused by the same process. Doctors should consider alcohol intake, medicines, viral hepatitis and other possible causes before assuming that the condition is entirely metabolic.

What is MASH?

Some people have fat in the liver without significant ongoing injury. Others develop inflammation and damage to liver cells. This more active form is called metabolic dysfunction-associated steatohepatitis, or MASH.

MASH was previously called non-alcoholic steatohepatitis, or NASH. It carries a greater risk of fibrosis, cirrhosis and liver-related complications than simple steatosis.

A scan can detect fat and sometimes estimate scarring, but it cannot always prove whether active inflammation is present. A liver biopsy is occasionally required when the diagnosis or severity remains uncertain.

What are the stages of fatty liver disease?

Fatty liver disease is often described as a progression through several stages. Not everyone moves through every stage, and the condition can sometimes improve when the underlying metabolic risk factors are treated.

Simple fatty liver or steatosis

At this stage, excess fat is present in the liver, but there is little or no inflammation and no significant scarring.

This is the most common form. Many people remain at this stage for years without developing serious liver problems. Nevertheless, it is an important warning sign because the same metabolic factors affecting the liver also raise the risk of type 2 diabetes, heart disease and stroke.

MASH or steatohepatitis

The liver contains excess fat and has also become inflamed. Liver cells may be injured or swollen.

MASH is more likely than simple steatosis to progress to fibrosis, although the rate varies considerably between individuals.

Fibrosis

Fibrosis means scar tissue has begun to form in response to persistent liver injury. The liver may still perform its normal functions, and a person may have no obvious symptoms.

Fibrosis is usually graded from mild to advanced. Identifying it early is important because reducing weight, improving diabetes control and treating cardiovascular risk factors may slow, stop or sometimes partly reverse the process.

Cirrhosis

Cirrhosis is advanced, widespread scarring that changes the structure of the liver. At first, the liver may continue to work reasonably well. This is called compensated cirrhosis.

If the liver can no longer perform its functions adequately, complications can develop. These may include fluid in the abdomen, internal bleeding, confusion, jaundice and a higher risk of liver cancer.

Progression is not inevitable. Many people with fatty liver never develop cirrhosis. Risk is higher when significant fibrosis is already present, particularly in people with type 2 diabetes, persistent obesity or multiple metabolic risk factors.

What causes fatty liver disease?

MASLD develops through a combination of metabolic, genetic and lifestyle influences. It is not simply the result of eating too much dietary fat.

When the body becomes less responsive to insulin, more fatty acids may be released into the bloodstream and delivered to the liver. The liver may also create and store more fat than it can process or export. This is known as insulin resistance and is central to the development of MASLD in many people.

The strongest associations include:

• overweight and obesity, especially excess fat around the abdomen;
• type 2 diabetes;
• prediabetes and insulin resistance;
• high triglycerides or abnormal cholesterol levels;
• high blood pressure;
• metabolic syndrome;
• polycystic ovary syndrome;
• obstructive sleep apnoea;
• low levels of physical activity;
• a diet high in excess calories, refined carbohydrates and sugary drinks.

Having one of these factors does not mean that liver disease will definitely develop. Likewise, fatty liver can occur in people who are not visibly overweight.

Can slim people develop fatty liver?

Yes. Some people with MASLD have a body mass index within the healthy range. They may still have insulin resistance, increased abdominal or internal fat, abnormal blood sugar, high triglycerides or a genetic susceptibility to storing fat in the liver.

Body mass index cannot show where fat is stored or reliably measure metabolic health. A person should not be told that fatty liver is impossible simply because they appear slim.

Does alcohol cause MASLD?

MASLD is primarily associated with metabolic dysfunction rather than heavy alcohol use. However, alcohol can still add to liver injury.

Some people have both metabolic fatty liver and alcohol exposure. Newer terminology includes the category MetALD for people whose liver disease appears to involve both metabolic factors and alcohol intake.

It is important to give doctors an honest estimate of how much alcohol you drink. This is not about judgement. It helps determine the likely cause of liver damage and the safest treatment plan.

Can medicines cause a fatty liver?

Some medicines can contribute to fat accumulation or liver injury, although this is much less common than metabolic fatty liver disease. Examples may include corticosteroids, tamoxifen, amiodarone, methotrexate and certain specialist medicines.

Do not stop a prescribed medicine because you are worried about your liver. Speak to the prescribing clinician, who can review the benefits, risks, dose and possible alternatives.

What are the symptoms of fatty liver disease?

Most people with early MASLD have no symptoms. The condition is often found incidentally after:

• abnormal liver blood tests;
• an ultrasound performed for abdominal pain;
• tests for diabetes, cholesterol or another condition;
• a scan that happens to include the liver.

When symptoms do occur, they tend to be vague. They may include:

• persistent tiredness or low energy;
• feeling generally unwell;
• a dull ache or discomfort beneath the ribs on the right side;
• difficulty concentrating;
• reduced stamina.

These symptoms are not specific to liver disease. Tiredness, for example, can also be related to anaemia, thyroid disorders, sleep problems, depression, vitamin deficiency and many other conditions.

Right-sided upper abdominal discomfort also has several possible causes. Gallstones, stomach and bowel conditions, muscle pain and lung problems can all cause pain in or near this area. Our guide to abdominal pain by location explains some of the main alternatives.

Symptoms of advanced liver disease

Symptoms are more likely once substantial scarring or cirrhosis has developed. Possible warning signs include:

• yellowing of the skin or whites of the eyes;
• itchy skin;
• dark urine or unusually pale stools;
• swelling of the ankles and legs;
• a swollen abdomen caused by fluid;
• easy bruising or bleeding;
• loss of appetite or unintentional weight loss;
• muscle wasting and weakness;
• confusion, poor concentration or unusual sleepiness;
• vomiting blood or passing black stools.

These symptoms require prompt medical assessment. Vomiting blood, black stools, severe confusion or collapse are emergencies.

How is fatty liver disease diagnosed?

There is no single test that answers every question about fatty liver disease. Assessment usually has two aims:

1. to confirm or support the presence of fat in the liver; and
2. to estimate whether significant fibrosis or cirrhosis is present.

A GP or specialist may review:

• weight and waist measurement;
• blood pressure;
• alcohol intake;
• current medicines and supplements;
• diabetes and cholesterol history;
• family history of liver disease;
• signs or symptoms of advanced liver disease.

Liver blood tests

Liver blood tests commonly include ALT, AST, ALP, GGT, bilirubin, albumin and sometimes clotting tests.

ALT and AST can rise when liver cells are irritated or damaged. GGT may be raised in fatty liver, alcohol-related liver disease and several other conditions. Albumin, bilirubin and clotting results can provide information about how well the liver is functioning, particularly when disease is advanced.

However, routine liver enzymes cannot measure fibrosis reliably. A person can have normal ALT and AST results while still having fatty liver or clinically important scarring. NICE specifically advises that routine liver blood tests should not be used to rule out NAFLD.

Our guides to liver function test results and ALT, AST, ALP and GGT explain what the individual markers can and cannot show.

Ultrasound

An abdominal ultrasound can often detect moderate or substantial fat in the liver. The liver may appear brighter than expected on the scan.

Ultrasound is widely available and does not use radiation. It can also assess the gallbladder, bile ducts and other abdominal organs.

Its limitations are important. Ultrasound may miss mild steatosis and cannot reliably determine whether the liver is inflamed. A conventional ultrasound also cannot precisely stage fibrosis.

Read more in our guide to what an abdominal ultrasound can show.

Fibrosis scores

Doctors increasingly use non-invasive fibrosis scores to estimate the likelihood of significant liver scarring.

The FIB-4 score uses:

• age;
• AST level;
• ALT level;
• platelet count.

A low result may suggest a low probability of advanced fibrosis. A higher or indeterminate result may lead to further testing or specialist referral.

FIB-4 has limitations and must be interpreted carefully, particularly in younger adults, older people and during acute illness. It is a risk-assessment tool rather than a diagnosis.

NICE guidance also discusses the enhanced liver fibrosis test, usually abbreviated to ELF. This blood test measures markers associated with the process of liver scarring. Availability varies across the NHS.

FibroScan and liver stiffness measurements

A FibroScan is a type of transient elastography. It sends a painless vibration through the liver and measures how quickly the wave travels.

A stiffer liver may indicate more fibrosis, although inflammation, congestion and other factors can sometimes affect the result. The machine may also estimate the amount of liver fat.

FibroScan is quick, non-invasive and increasingly used after an abnormal fibrosis score. It is not identical to an ordinary ultrasound.

MRI and CT scans

MRI-based techniques can measure liver fat and stiffness with greater precision, but they are more expensive and not needed for every patient.

CT scans may show fatty liver incidentally, but CT is not generally the preferred first-line test solely for diagnosing MASLD because it uses ionising radiation and is less sensitive for mild fat accumulation.

Liver biopsy

A liver biopsy involves removing a very small sample of liver tissue through a needle so it can be examined under a microscope.

It can show the degree of fat, inflammation and fibrosis and remains the most direct way to confirm MASH. However, it is invasive and carries small risks, so it is normally reserved for selected cases where the diagnosis is uncertain or the result would materially change treatment.

Who is most at risk of liver scarring?

Many people with fatty liver have a low risk of advanced disease. Others require closer follow-up because fibrosis can progress silently.

The risk of significant fibrosis is higher in people with:

• type 2 diabetes;
• severe or long-standing obesity;
• several features of metabolic syndrome;
• older age;
• persistently abnormal liver blood tests;
• obstructive sleep apnoea;
• a family history of cirrhosis or liver disease;
• regular alcohol consumption alongside metabolic risk factors;
• evidence of fibrosis on blood tests or elastography.

Type 2 diabetes is particularly important. It increases the likelihood of MASH, fibrosis and cardiovascular disease. People with diabetes may therefore be assessed for liver fibrosis even when they have no liver-related symptoms.

Our guide to diabetes symptoms, tests and treatment provides a broader explanation of how blood sugar disorders affect health.

Is fatty liver itself dangerous?

Simple fat accumulation is not the same as liver failure and should not automatically cause alarm. The main long-term concern is whether the condition progresses to inflammation and fibrosis.

It is also important to look beyond the liver. People with MASLD are often more likely to develop cardiovascular disease. In many patients, heart attack and stroke represent a greater overall health risk than liver failure.

Managing blood pressure, cholesterol, blood sugar, smoking and physical inactivity is therefore part of liver treatment rather than a separate issue.

How is fatty liver disease treated?

Treatment depends on the stage of liver disease and the person’s wider metabolic health. For most people, the foundation of treatment is gradual, sustainable improvement in weight, diet, physical activity and associated conditions.

There is no detox drink, supplement or crash diet that can safely remove liver fat overnight.

Weight loss

For people who are overweight, losing weight can reduce liver fat and improve metabolic health. Greater sustained weight loss may also improve liver inflammation and fibrosis.

The aim should usually be gradual, maintainable weight reduction rather than repeated cycles of severe restriction and regain. Even a modest loss can improve blood sugar, blood pressure and triglycerides.

The most appropriate target depends on starting weight, age, health conditions and whether advanced liver disease is present. People with cirrhosis or significant muscle loss need specialist dietary advice because poorly planned calorie restriction can worsen malnutrition.

Our guide to how weight loss works explains energy balance and why sustainable changes matter more than quick fixes.

Diet

There is no single mandatory “fatty liver diet”. The most useful pattern is generally one that improves overall metabolic health and can be maintained long term.

This usually means eating more:

• vegetables and fruit;
• beans, lentils and other pulses;
• wholegrain or higher-fibre carbohydrates;
• fish and lean sources of protein;
• nuts and seeds in sensible portions;
• unsaturated fats such as olive or rapeseed oil.

It is also sensible to reduce:

• sugary drinks;
• frequent sweets, cakes and desserts;
• large portions of refined carbohydrates;
• highly processed foods;
• excess saturated fat;
• regular overeating, even of foods marketed as healthy.

Sugary drinks are particularly easy to consume without feeling full. Fruit juice, sweetened coffee, energy drinks and fizzy drinks can add a substantial amount of sugar and energy.

A Mediterranean-style eating pattern is often recommended because it is rich in vegetables, fibre, whole foods and unsaturated fats and can improve cardiovascular risk factors.

Exercise

Physical activity can reduce liver fat and improve insulin sensitivity even when weight loss is modest.

A balanced plan may include:

• brisk walking, cycling, swimming or another aerobic activity;
• strength or resistance exercise several times a week;
• breaking up long periods of sitting;
• gradually increasing activity rather than attempting an unsustainable programme.

People who have been inactive, have heart symptoms or live with several medical conditions should seek advice before beginning vigorous exercise.

Managing diabetes, cholesterol and blood pressure

Good control of type 2 diabetes can reduce metabolic stress and may lower the risk of progression. Blood pressure and cholesterol treatment reduces cardiovascular risk, which is a central part of managing MASLD.

Statins are often safe for people with fatty liver disease when they are clinically indicated. Having MASLD is not in itself a reason to avoid cholesterol-lowering treatment. Monitoring may be needed depending on liver results and the medicine used.

Our guide to statins, their benefits and side effects explains this treatment in more detail.

Weight-loss medicines and diabetes treatments

Some medicines used for obesity and type 2 diabetes can produce substantial weight loss and improve metabolic risk factors. GLP-1-based treatments, including semaglutide, and dual-action medicines such as tirzepatide may reduce liver fat as weight and blood sugar improve.

They are not suitable for everyone and should be prescribed within an appropriate clinical pathway. The decision should consider eligibility, side effects, other conditions and the need for long-term treatment.

Read our guide to weight-loss injections and diabetes for a fuller explanation.

Medicines specifically for MASH

Treatment options for MASH are developing. Availability and licensing differ between countries, and specialist medicines may only be suitable for people with confirmed inflammation and a particular stage of fibrosis.

In UK practice, treatment still centres largely on weight management, cardiovascular risk reduction and control of diabetes and other metabolic conditions. A liver specialist can advise whether clinical trials or emerging treatments are relevant.

Alcohol

Alcohol is not the defining cause of MASLD, but it can add to liver injury. People with fibrosis, MASH or cirrhosis may be advised to avoid alcohol completely.

For others, the safest limit depends on the degree of liver damage, other medical conditions and drinking pattern. Ask the treating clinician for individual advice rather than assuming that national low-risk limits are automatically safe for an already affected liver.

Smoking

Smoking increases cardiovascular and cancer risks and may compound the wider health burden associated with metabolic disease. Stopping smoking is one of the most valuable steps a person can take for long-term health.

Can fatty liver disease be reversed?

Simple fatty liver can often improve substantially when the metabolic drivers are addressed. Liver fat can decrease with sustained weight loss, regular activity, better diabetes control and reduced alcohol exposure.

Inflammation and early fibrosis may also improve in some people. The liver has a considerable capacity to repair itself when the cause of injury is reduced.

Advanced cirrhosis is much less likely to reverse completely because the liver architecture has already been extensively altered. Even then, treatment remains worthwhile. It can reduce further damage, lower complication risk and improve overall health.

The word “reversed” should not be understood as permanent immunity. Liver fat can return if weight, blood sugar or other risk factors worsen again.

How quickly can liver fat improve?

Changes in liver fat may occur over weeks or months, but long-term risk is determined by sustained habits and fibrosis rather than a single short-term result.

Rapid weight loss is not always better. Very restrictive diets can cause nutritional problems, muscle loss and, in some circumstances, worsen gallstone risk. A structured approach is safer, particularly for people with diabetes, older adults and anyone with advanced liver disease.

Do liver detoxes work?

There is no good evidence that commercial detox drinks, teas or cleanses remove liver fat or fibrosis.

Some herbal products and supplements can injure the liver or interact with prescribed medicines. “Natural” does not necessarily mean safe. Tell your doctor or pharmacist about any supplements you take.

How is fatty liver monitored?

Follow-up should reflect fibrosis risk rather than simply repeating an ultrasound every year.

Monitoring may include:

• weight and waist measurement;
• blood pressure;
• HbA1c or other blood sugar tests;
• cholesterol and triglycerides;
• liver blood tests;
• platelet count;
• a repeat FIB-4, ELF test or FibroScan when appropriate;
• review of alcohol, medicines and lifestyle changes.

People at low risk of fibrosis may be monitored in primary care. Those with indeterminate or high-risk results may be referred to hepatology or gastroenterology.

Anyone with cirrhosis requires specialist follow-up. This may include regular ultrasound surveillance for liver cancer, checks for enlarged veins in the oesophagus and management of complications.

When should you speak to a GP?

Arrange a GP appointment if:

• a scan has reported fatty liver and no follow-up plan has been discussed;
• liver blood tests remain abnormal;
• you have type 2 diabetes and are concerned about liver risk;
• you have persistent discomfort under the right ribs;
• you develop unexplained tiredness, appetite loss or weight loss;
• you are unsure whether alcohol or medicines may be affecting your liver;
• you have been told you have fibrosis or a high liver stiffness result.

Seek urgent advice for jaundice, increasing abdominal swelling, marked drowsiness, confusion or signs of internal bleeding.

Frequently asked questions about fatty liver disease

Is MASLD the same as NAFLD?

MASLD is the newer name for what was usually called NAFLD. The diagnostic framework has changed slightly, but in ordinary patient information the terms generally describe the same metabolic fatty liver condition. You may encounter both names in NHS records and medical literature.

Is fatty liver disease serious?

It can be, but severity varies. Many people have simple steatosis without advanced damage. The main concern is whether inflammation and fibrosis are present. Fibrosis assessment is therefore more informative than the presence of fat alone.

Can you have fatty liver with normal liver blood tests?

Yes. ALT and AST may be normal even when fat or significant fibrosis is present. Routine liver blood tests should not be used on their own to rule out MASLD.

What does a bright liver on ultrasound mean?

A bright or echogenic liver often suggests fat accumulation. Ultrasound cannot reliably show whether inflammation is present or precisely measure fibrosis, so further risk assessment may be needed.

Does fatty liver cause pain?

It can cause a dull ache or discomfort beneath the right ribs, but most people have no pain. Severe or sudden abdominal pain is not typical and should be assessed for other causes.

Can fatty liver make you tired?

Fatigue is reported by some people with MASLD, but it has many possible causes. Anaemia, thyroid disease, poor sleep, vitamin deficiency and mental health conditions may also need consideration.

Can thin people get MASLD?

Yes. Genetic factors, abdominal fat, insulin resistance, diabetes and abnormal cholesterol can contribute even when body mass index is not elevated.

Should I stop eating all fat?

No. The body needs dietary fat, and unsaturated fats can form part of a healthy diet. The overall calorie intake and dietary pattern matter more than eliminating every source of fat.

Is sugar worse than fat for fatty liver?

Both excess calories and poor overall diet can contribute. Sugary drinks and frequent refined carbohydrates can promote weight gain and liver fat because they are easy to overconsume. Saturated fat may also worsen metabolic health. The best approach is a balanced, minimally processed diet rather than focusing on a single nutrient.

Can coffee help fatty liver disease?

Research has associated regular coffee consumption with a lower risk of fibrosis and some chronic liver complications. However, coffee is not a treatment by itself, and sugary syrups or high-calorie additions may undermine metabolic goals. People who cannot tolerate caffeine should not feel obliged to drink it.

Can I drink alcohol if I have fatty liver?

The answer depends on whether fibrosis or cirrhosis is present, how much you drink and your wider health. Alcohol can add to liver damage. Ask your clinician for individual advice; people with advanced fibrosis or cirrhosis may be advised not to drink at all.

Do statins make fatty liver worse?

Statins do not generally need to be avoided simply because someone has MASLD. They may be important for reducing heart attack and stroke risk. Liver tests may be monitored, and treatment decisions should be made with the prescribing clinician.

Can fatty liver turn into cancer?

Advanced fibrosis and cirrhosis increase the risk of hepatocellular carcinoma, the most common primary liver cancer. The absolute risk is much lower in simple fatty liver without advanced fibrosis.

Can children develop fatty liver disease?

Yes. MASLD can occur in children and young people, particularly alongside obesity, insulin resistance and type 2 diabetes. Assessment and treatment should involve clinicians experienced in paediatric liver and metabolic health.

Will losing weight cure fatty liver?

Sustained weight loss can substantially reduce liver fat and may improve inflammation and early fibrosis. The condition can return if metabolic risk factors return, so long-term maintenance is important.

Which doctor treats fatty liver disease?

Low-risk MASLD is often managed by a GP alongside diabetes, weight, blood pressure and cholesterol. People with suspected advanced fibrosis, cirrhosis or an uncertain diagnosis may be referred to a hepatologist or gastroenterologist.