The COVID-19 pandemic has revealed that SARS-CoV-2 infection affects multiple organ systems beyond the lungs, including the liver. Fatty liver disease, or hepatic steatosis, occurs when excess fat accumulates in liver cells and is increasingly common in the UK, affecting approximately one in three adults. Research has documented elevated liver enzymes in 14–53% of hospitalised COVID-19 patients, raising questions about whether the virus can cause or worsen fatty liver disease. Whilst associations between COVID-19 and liver metabolism changes have been observed, establishing direct causation remains an area of ongoing investigation. Understanding this complex relationship is important for patients recovering from COVID-19 and healthcare professionals monitoring potential long-term complications.

Understanding Fatty Liver Disease and COVID-19

Fatty liver disease, medically termed hepatic steatosis, occurs when excess fat accumulates in liver cells. This condition exists in two main forms: non-alcoholic fatty liver disease (NAFLD)—also increasingly referred to as metabolic dysfunction-associated steatotic liver disease (MASLD) in newer literature—which affects people who drink little or no alcohol, and alcohol-related liver disease (ARLD), linked to excessive alcohol consumption. NAFLD has become increasingly common in the UK, affecting approximately one in three adults, often associated with obesity, type 2 diabetes, and metabolic syndrome.

Since the COVID-19 pandemic began, researchers have observed that SARS-CoV-2 infection can affect multiple organ systems beyond the respiratory tract. The liver, being a vital metabolic organ, has emerged as a potential target. Studies have documented elevated liver enzymes—particularly alanine aminotransferase (ALT) and aspartate aminotransferase (AST)—in 14–53% of hospitalised COVID-19 patients, indicating some degree of liver involvement during acute infection. These abnormalities are often mild and transient, and may result from multiple factors including systemic inflammation, reduced oxygen supply (hypoxia), immune responses, and medication effects, rather than direct viral injury to liver cells alone.

The relationship between COVID-19 and fatty liver disease is complex and bidirectional. People with pre-existing NAFLD may experience worse COVID-19 outcomes, whilst the infection itself may be associated with changes in liver metabolism and fat accumulation through various mechanisms. Understanding this connection is important for both patients recovering from COVID-19 and healthcare professionals monitoring long-term complications.

It is important to note that whilst associations have been observed, establishing direct causation remains an area of ongoing research. The interplay between viral infection, inflammation, metabolic changes, and liver health continues to be investigated by the medical community.

Can COVID-19 Cause or Worsen Fatty Liver?

Current evidence suggests that COVID-19 may be associated with the development or worsening of fatty liver disease through several potential mechanisms, though there is no definitive proof of direct causation. Observational studies have documented changes in liver metabolism during and after infection, but distinguishing the virus's direct effects from those of associated factors—such as reduced physical activity during illness, weight gain during isolation, or treatments including corticosteroids—remains challenging.

During acute COVID-19 infection, the liver may experience systemic inflammation, with release of cytokines that can affect liver metabolism and potentially promote fat accumulation. COVID-19 infection often leads to metabolic disturbances, including insulin resistance and altered lipid metabolism, both of which are key drivers of hepatic steatosis. Additionally, the liver may be affected by hypoxia (reduced oxygen supply) in severe cases and, occasionally, by drug-induced liver injury from medications used in treatment. Whilst typical corticosteroid courses for COVID-19 (such as dexamethasone) are short, they may contribute to metabolic changes during the acute illness and recovery period.

Research published in peer-reviewed journals has documented new-onset fatty liver changes in some patients following COVID-19, detected through imaging studies and liver function tests. However, these findings are largely observational, and multiple confounding factors—including changes in diet, physical activity, and weight—make it difficult to attribute these changes solely to the virus itself.

Post-COVID syndrome (long COVID) has also been associated with persistent metabolic abnormalities. Some patients report ongoing fatigue, reduced exercise capacity, and weight changes that may indirectly contribute to liver fat accumulation over time. Studies have shown that inflammatory markers can remain elevated months after initial infection, though the long-term implications for liver health require further longitudinal research.

For individuals with pre-existing NAFLD, COVID-19 infection may potentially accelerate disease activity. The combination of baseline liver inflammation and acute viral stress could theoretically advance simple steatosis towards non-alcoholic steatohepatitis (NASH), a more severe form involving liver inflammation and damage. However, robust evidence for this progression is limited, and the long-term relationship between COVID-19 and chronic liver disease development remains an area of active investigation.

Vaccination against COVID-19 and timely treatment of severe infection may reduce the risks of complications that could indirectly affect liver health.

Risk Factors for Liver Problems After COVID-19

Several factors may increase the likelihood of developing liver-related complications following COVID-19 infection. Pre-existing metabolic conditions represent the most significant risk category, including:

• Obesity (BMI ≥30 kg/m²), which independently increases both COVID-19 severity and NAFLD risk

• Type 2 diabetes mellitus, affecting glucose and lipid metabolism

• Metabolic syndrome, characterised by central obesity, hypertension, dyslipidaemia, and insulin resistance

• Pre-existing liver disease, including NAFLD, chronic hepatitis, or cirrhosis

Severity of COVID-19 infection correlates with liver involvement. Patients requiring hospitalisation, intensive care admission, or mechanical ventilation show higher rates of liver enzyme abnormalities and potential for metabolic disturbance. Elevated inflammatory markers such as C-reactive protein (CRP) and ferritin are associated with severe COVID-19, though their value in predicting long-term liver outcomes remains uncertain.

Medication exposure during COVID-19 treatment can affect liver health. Certain antivirals and antibiotics may occasionally cause liver enzyme changes. Corticosteroids such as dexamethasone, whilst typically given for short courses in severe COVID-19, may influence metabolism during illness and recovery. The overall metabolic stress of severe infection, rather than individual medications alone, likely contributes most to liver-related risk.

Lifestyle factors during and after infection play important roles. Extended periods of reduced physical activity during illness or isolation, coupled with dietary changes and potential weight gain, create conditions favouring hepatic steatosis. Additionally, increased alcohol consumption—reported by some individuals during lockdowns—compounds liver stress. The UK Chief Medical Officers advise that to keep health risks from alcohol low, it is safest not to drink more than 14 units per week on a regular basis, spread over three or more days.

Age influences risk, with older adults showing higher rates of severe liver involvement during COVID-19. Epidemiological studies also suggest that men may experience more severe COVID-19 outcomes, though the specific impact on long-term liver health requires further research.

When to Seek Medical Advice About Liver Health

Recognising when to contact your GP regarding potential liver problems after COVID-19 is essential for early detection and management. The liver often develops problems silently, without obvious symptoms in early stages, making awareness of subtle signs particularly important. It is also worth noting that liver enzymes (ALT and AST) can be normal in people with NAFLD, so decisions about further assessment should not rely on these tests alone.

Contact your GP if you experience:

• Persistent fatigue or weakness that doesn't improve weeks after COVID-19 recovery

• Unexplained weight gain, particularly around the abdomen

• Discomfort or a feeling of fullness in the upper right abdomen

• Yellowing of the skin or whites of the eyes (jaundice)

• Dark urine or pale stools

• Persistent nausea or loss of appetite

• Easy bruising or bleeding

• Itchy skin without obvious cause

Seek urgent medical attention (contact 111 or attend A&E) if you develop:

• Severe abdominal pain

• Vomiting blood or passing black, tarry stools

• Confusion or marked drowsiness

• Jaundice (yellowing of skin or eyes)

• Increasing abdominal swelling or leg swelling

These may indicate serious liver complications or decompensation requiring immediate assessment.

For patients with known risk factors—such as pre-existing NAFLD, diabetes, or obesity—who have recovered from COVID-19, proactive monitoring is advisable. Your GP may recommend blood tests to check liver function (ALT, AST, gamma-GT, and alkaline phosphatase) and metabolic markers. According to NICE guideline NG49 on non-alcoholic fatty liver disease, adults with suspected NAFLD should first have their risk of advanced liver fibrosis assessed using a validated scoring system such as the FIB-4 score or the NAFLD Fibrosis Score. If these suggest possible advanced fibrosis, the Enhanced Liver Fibrosis (ELF) blood test may be used to further assess fibrosis risk. Ultrasound scanning can detect liver fat (steatosis) but does not stage fibrosis. In specialist settings, transient elastography (FibroScan) may be used to assess liver stiffness and fibrosis.

Regular health monitoring should include tracking weight, blood pressure, and blood glucose levels. Lifestyle modifications form the cornerstone of NAFLD management and may help mitigate any COVID-19-related liver effects. These include:

• A balanced Mediterranean-style diet rich in vegetables, fruits, whole grains, oily fish, and healthy fats

• Regular physical activity, aiming for at least 150 minutes of moderate-intensity exercise weekly

• Gradual weight loss if overweight (a target of 7–10% body weight can improve liver health)

• Limiting alcohol consumption to no more than 14 units per week, spread over three or more days, with several alcohol-free days each week

Your GP can provide personalised advice and, if necessary, refer you to hepatology services for specialist assessment and ongoing care.

If you experience side effects from any medication (including treatments received for COVID-19), you can report these via the MHRA Yellow Card Scheme at yellowcard.mhra.gov.uk or through the Yellow Card app.

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