Wegovy Liver Enzymes: Monitoring and Safety Guidance

Wegovy (semaglutide) is a once-weekly GLP-1 receptor agonist licensed in the UK for weight management in adults with obesity or overweight with comorbidities. As with any medication metabolised by the liver, questions about Wegovy liver enzymes and potential hepatic effects are common. Current evidence suggests that clinically significant liver enzyme elevations are uncommon with Wegovy. In fact, the weight loss achieved with semaglutide may improve liver enzyme levels in individuals with non-alcoholic fatty liver disease (NAFLD). This article examines the relationship between Wegovy and liver function, monitoring recommendations, and when to seek medical advice.

What Is Wegovy and How Does It Work?

Wegovy (semaglutide) is a prescription medicine licensed in the UK for weight management in adults with obesity (BMI ≥30 kg/m²) or overweight (BMI ≥27 kg/m²) with at least one weight-related comorbidity, such as type 2 diabetes, hypertension, or obstructive sleep apnoea. It is administered as a once-weekly subcutaneous injection, starting with a lower dose that is gradually increased over several weeks to a target dose of 2.4 mg, and should be used alongside a reduced-calorie diet and increased physical activity.

Semaglutide belongs to a class of medications called glucagon-like peptide-1 (GLP-1) receptor agonists. It works by mimicking the action of the naturally occurring hormone GLP-1, which is released from the intestine after eating. By binding to GLP-1 receptors in the brain, particularly in areas that regulate appetite, Wegovy helps to reduce hunger and increase feelings of fullness. This leads to a reduction in calorie intake and, consequently, weight loss.

Additionally, semaglutide slows gastric emptying, meaning food remains in the stomach for longer, which contributes to prolonged satiety. It also has beneficial effects on blood glucose control by stimulating insulin secretion in a glucose-dependent manner and suppressing glucagon release, although it's important to note that Wegovy is specifically licensed for weight management, not for the treatment of hyperglycaemia.

Clinical trials have demonstrated that Wegovy can lead to significant weight loss—typically around 10–15% of initial body weight over 68 weeks—when combined with lifestyle modifications. While Wegovy is MHRA-licensed in the UK, access through the NHS is more restricted. NICE guidance (TA875) recommends semaglutide only within specialist weight management services, with narrower BMI and comorbidity criteria than the licence, and for a time-limited period.

Can Wegovy Affect Liver Enzymes?

Concerns about the potential impact of weight-loss medications on liver function are understandable, given that the liver plays a central role in drug metabolism. Current evidence suggests that clinically significant liver enzyme elevations are uncommon with Wegovy. Serious drug-induced liver injury is very rare, though a few post-marketing cases have been reported where causality has not been established.

It is important to distinguish between drug-induced liver effects and the beneficial impact that weight loss itself can have on liver health. Many individuals with obesity have non-alcoholic fatty liver disease (NAFLD), a condition characterised by fat accumulation in the liver that can lead to elevated liver enzymes (particularly alanine aminotransferase, or ALT). Studies have shown that significant weight loss—such as that achieved with Wegovy—can improve liver enzyme levels and reduce hepatic steatosis in patients with NAFLD, though these biochemical improvements do not necessarily confirm histological resolution of steatohepatitis or fibrosis.

In the STEP (Semaglutide Treatment Effect in People with obesity) clinical trial programme, participants treated with semaglutide experienced improvements in markers of liver health, including reductions in ALT and aspartate aminotransferase (AST). These findings suggest that Wegovy may have a beneficial effect on the liver through weight reduction and improved metabolic parameters.

It's worth noting that GLP-1 receptor agonists, including semaglutide, are associated with an increased risk of gallbladder disease (for example, cholelithiasis and cholecystitis). According to the Summary of Product Characteristics (SmPC), no dose adjustment is required in hepatic impairment, though experience in severe hepatic impairment is limited and clinical monitoring is advised.

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Monitoring Liver Function While Taking Wegovy

Routine monitoring of liver enzymes is not mandated in the SmPC for all patients taking Wegovy, as the medication is not associated with a high risk of hepatotoxicity. However, healthcare professionals may recommend baseline liver function tests (LFTs) before starting treatment, particularly in individuals with known risk factors for liver disease, such as obesity, type 2 diabetes, excessive alcohol consumption, or a history of viral hepatitis.

Baseline liver function tests usually include measurements of:

• Alanine aminotransferase (ALT) and aspartate aminotransferase (AST): enzymes that indicate liver cell damage when elevated

• Alkaline phosphatase (ALP): an enzyme that may be raised in bile duct obstruction or liver disease

• Bilirubin: a breakdown product of red blood cells; elevated levels can indicate liver dysfunction or bile duct problems

• Albumin: a protein made by the liver; low levels may suggest chronic liver disease

For most patients without pre-existing liver conditions, repeat LFTs during Wegovy treatment are not routinely necessary unless symptoms suggestive of liver dysfunction develop. However, individuals with non-alcoholic fatty liver disease (NAFLD) or non-alcoholic steatohepatitis (NASH) may benefit from periodic monitoring to assess improvements in liver health as weight loss progresses. In line with NICE guideline NG49, non-invasive fibrosis risk stratification (such as FIB-4 or ELF tests) may be appropriate.

If ALT/AST levels exceed 3 times the upper limit of normal, if bilirubin is rising, if there is a cholestatic pattern (raised ALP/GGT with jaundice), or if symptomatic liver disease develops, arrange urgent assessment and consider stopping treatment pending evaluation.

Your prescribing clinician will determine the appropriate monitoring schedule based on your individual medical history and risk profile. If you have concerns about liver function or experience unexplained symptoms, do not hesitate to request a review. It is also important to attend all scheduled follow-up appointments, as these provide an opportunity to assess treatment response, manage side effects, and adjust the dose if necessary.

When to Seek Medical Advice About Liver Health

While serious liver-related side effects appear very rare with Wegovy, it is important to be aware of symptoms that may indicate liver dysfunction and warrant prompt medical attention. Contact your GP for a same-day appointment or call NHS 111 if you experience any of the following:

• Jaundice: yellowing of the skin or whites of the eyes

• Dark urine: urine that appears brown or tea-coloured

• Pale stools: stools that are unusually light or clay-coloured

• Persistent nausea or vomiting: especially if accompanied by abdominal pain

• Severe or persistent abdominal pain: particularly in the upper right side, which may indicate liver or gallbladder issues

• Unexplained fatigue or weakness: that is new or worsening

• Loss of appetite: especially if accompanied by other symptoms

Call 999 or go to A&E for severe abdominal pain, jaundice with confusion, or if you feel seriously unwell.

These symptoms could indicate a range of conditions, including liver inflammation, bile duct obstruction, or gallbladder disease (such as cholecystitis or cholelithiasis, which can occur with rapid weight loss and are known risks with GLP-1 receptor agonists). If symptoms occur, seek prompt assessment.

If you have a pre-existing liver condition, such as chronic hepatitis, cirrhosis, or NAFLD, inform your prescribing clinician before starting Wegovy. They may recommend more frequent monitoring or additional investigations, such as liver ultrasound or FibroScan, to assess liver health over time.

It is also worth noting that pancreatitis—inflammation of the pancreas—has been reported in some patients taking GLP-1 receptor agonists. Symptoms include severe, persistent abdominal pain that may radiate to the back, often accompanied by nausea and vomiting. If you experience these symptoms, stop taking Wegovy and seek urgent medical attention, as pancreatitis requires prompt investigation and management. Always keep your healthcare team informed of any side effects or health changes while taking Wegovy.

Report any suspected side effects to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).

Frequently Asked Questions