Asthma and non-alcoholic fatty liver disease (NAFLD)—now increasingly termed metabolic dysfunction-associated steatotic liver disease (MASLD)—are two prevalent conditions that may be more connected than previously recognised. Asthma affects approximately 5.4 million people in the UK, whilst NAFLD is estimated to affect up to one in three adults. Emerging evidence suggests individuals with asthma may have a higher prevalence of fatty liver disease, though the relationship appears multifactorial rather than directly causal. Shared risk factors including obesity, chronic inflammation, metabolic syndrome, and certain asthma treatments—particularly oral corticosteroids—may contribute to this association. Understanding this potential link is important for holistic patient care and early intervention.

Understanding the Link Between Asthma and Fatty Liver Disease

Asthma and non-alcoholic fatty liver disease (NAFLD)—increasingly referred to as metabolic dysfunction-associated steatotic liver disease (MASLD)—are two common conditions that may share more than coincidental overlap. Asthma affects approximately 5.4 million people in the UK, whilst NAFLD is estimated to affect up to one in three adults. Emerging research suggests that individuals with asthma may have a higher prevalence of fatty liver disease compared to the general population, though no direct causal link has been established between the two conditions.

The relationship appears to be multifactorial rather than straightforward. Both conditions are associated with chronic systemic inflammation, which may create a biological environment that promotes the development of each disease. Studies have observed that people with poorly controlled asthma, particularly those requiring frequent corticosteroid use, may be at increased risk of developing metabolic complications including fatty liver disease. However, it remains unclear whether asthma itself directly causes liver fat accumulation or whether shared risk factors—such as obesity, physical inactivity, and metabolic syndrome—and certain treatments contribute to this association.

Key considerations include:

• Both conditions involve inflammatory pathways that may interact

• Obesity is a significant risk factor for both asthma and NAFLD

• Certain asthma medications, particularly oral corticosteroids, may influence metabolic health

• Reduced physical activity due to respiratory symptoms may contribute to weight gain and metabolic dysfunction

Understanding this potential connection is important for holistic patient care. It is important to note that early NAFLD is often asymptomatic and liver function tests (LFTs) may be normal. Healthcare professionals should assess liver health based on recognised NAFLD risk factors—such as obesity, type 2 diabetes, and metabolic syndrome—rather than asthma alone. Similarly, individuals with fatty liver disease who develop respiratory symptoms should receive appropriate asthma assessment and management according to NICE guidelines (NG80).

References:

• NICE NG80: Asthma: diagnosis, monitoring and chronic asthma management

• NICE NG49: Non-alcoholic fatty liver disease: assessment and management

• NHS: Non-alcoholic fatty liver disease (NAFLD)

How Asthma Medications May Affect Liver Health

Asthma medications are generally safe and well-tolerated, but certain treatments may have implications for liver health, particularly with long-term use. Corticosteroids, both inhaled and oral, are cornerstone treatments for asthma management but can influence metabolic processes that affect the liver.

Oral corticosteroids (such as prednisolone) are known to affect glucose metabolism and can promote insulin resistance, weight gain, and fat redistribution—all factors that may contribute to the development or worsening of fatty liver disease. Long-term or frequent courses of oral steroids may increase the risk of metabolic syndrome, which is closely linked to NAFLD. The MHRA advises that oral corticosteroids should be used at the lowest effective dose for the shortest duration necessary, with regular review of the need for continued treatment. NICE guidance (NG80) emphasises steroid-sparing strategies, including optimising inhaled therapy and considering add-on treatments or biologic therapies to reduce reliance on oral steroids.

Inhaled corticosteroids (ICS), such as beclometasone or fluticasone, have significantly fewer systemic effects than oral preparations. However, high doses over prolonged periods may still have some metabolic impact, though the risk is substantially lower. The benefits of ICS in controlling asthma typically far outweigh potential metabolic risks.

Other asthma medications include:

• Leukotriene receptor antagonists (montelukast): Rare cases of hepatic adverse reactions have been reported. Routine liver function monitoring is not recommended, but patients should be advised to seek medical attention if they develop symptoms suggestive of liver injury (such as unexplained nausea, vomiting, abdominal pain, fatigue, jaundice, or dark urine). Clinicians should follow the Summary of Product Characteristics (SmPC) guidance.

• Long-acting beta-agonists (LABAs) and short-acting beta-agonists (SABAs): No significant direct hepatic effects.

• Long-acting muscarinic antagonists (LAMAs, such as tiotropium): Generally well-tolerated with no significant hepatic effects; used as add-on therapy in asthma per NICE guidance.

• Theophylline: Metabolised in the liver; caution is required in patients with hepatic impairment due to potential for drug interactions and altered clearance. Dose adjustment and monitoring may be necessary.

• Biologic therapies (including omalizumab, mepolizumab, reslizumab, benralizumab, dupilumab, and tezepelumab): Generally well-tolerated with minimal liver impact; routine hepatic monitoring is not required unless clinically indicated.

Patients on long-term asthma treatment, particularly those requiring frequent oral corticosteroids, should discuss liver health monitoring with their GP or respiratory specialist. This is especially important for individuals with additional risk factors for fatty liver disease, such as obesity, type 2 diabetes, or metabolic syndrome.

Important: Do not stop or alter your asthma medication without consulting your healthcare professional. If you experience any suspected side effects from your medicines, report them via the MHRA Yellow Card scheme at https://yellowcard.mhra.gov.uk.

References:

• NICE NG80: Asthma: diagnosis, monitoring and chronic asthma management

• BNF: Asthma, acute and chronic management

• eMC SmPC: Montelukast, Prednisolone, inhaled corticosteroids

• MHRA Yellow Card Scheme

Shared Risk Factors: Inflammation, Obesity and Metabolic Syndrome

The intersection between asthma and fatty liver disease is significantly influenced by shared risk factors, particularly obesity, chronic inflammation, and metabolic syndrome. Understanding these common pathways is essential for comprehensive patient management.

Obesity is perhaps the most significant shared risk factor. In the UK, approximately 28% of adults are obese, and obesity is strongly associated with both conditions. Excess body weight, particularly visceral adiposity, promotes systemic inflammation and insulin resistance—key drivers of both asthma severity and NAFLD development. Research indicates that obese individuals with asthma often experience more severe symptoms, reduced response to standard treatments, and increased healthcare utilisation. Simultaneously, obesity is the primary risk factor for NAFLD, with estimates suggesting that a substantial proportion of obese individuals (ranging widely depending on diagnostic criteria and population studied) have some degree of liver fat accumulation.

Chronic systemic inflammation represents another crucial link. Both asthma and NAFLD are characterised by inflammatory processes, though affecting different organ systems. Inflammatory mediators such as interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), and C-reactive protein (CRP) are elevated in both conditions. This shared inflammatory state may create a self-perpetuating cycle where inflammation in one system exacerbates disease in another.

Metabolic syndrome—defined by the presence of central obesity, hypertension, dyslipidaemia, and insulin resistance—is strongly associated with both conditions. Studies suggest that individuals with metabolic syndrome have:

• Increased asthma prevalence and severity

• Higher risk of developing NAFLD and its progression to non-alcoholic steatohepatitis (NASH), now termed metabolic dysfunction-associated steatohepatitis (MASH)

• Greater likelihood of cardiovascular complications

Additional shared factors include:

• Physical inactivity (often due to respiratory limitations or reduced exercise tolerance)

• Dietary patterns high in processed foods and refined carbohydrates

• Sleep disturbances, including obstructive sleep apnoea

• Genetic predisposition to inflammatory and metabolic conditions

Alcohol intake should also be assessed when evaluating fatty liver disease, to differentiate NAFLD/MASLD from alcohol-related liver disease. The UK Chief Medical Officers advise that adults should not regularly drink more than 14 units of alcohol per week, spread over three or more days.

Addressing these shared risk factors through lifestyle modification can benefit both conditions simultaneously, making integrated care approaches particularly valuable.

References:

• NICE NG49: Non-alcoholic fatty liver disease: assessment and management

• Health Survey for England: Adult obesity statistics

• UK Chief Medical Officers' Low Risk Drinking Guidelines

Managing Both Conditions: Treatment Considerations in the UK

Managing patients with both asthma and fatty liver disease requires a coordinated, holistic approach that addresses both conditions whilst considering potential treatment interactions. NICE guidance provides frameworks for managing each condition, but individualised care is essential when both are present.

Asthma management should follow the NICE guideline (NG80), which recommends a stepwise approach. For patients with concurrent fatty liver disease, particular considerations include:

• Optimising inhaled therapy (inhaled corticosteroids with or without long-acting beta-agonists) to minimise the need for oral corticosteroids

• Considering add-on therapies such as leukotriene receptor antagonists (LTRA), long-acting muscarinic antagonists (LAMA, e.g., tiotropium), or maintenance and reliever therapy (MART) regimens to improve control

• Referral to specialist severe asthma services for patients requiring frequent oral steroids or with uncontrolled symptoms, to assess suitability for biologic therapies (such as omalizumab, mepolizumab, reslizumab, benralizumab, dupilumab, or tezepelumab)

• Regular asthma reviews to ensure control is achieved with the lowest effective medication doses

• Personalised asthma action plans to prevent exacerbations that might necessitate steroid courses

Fatty liver disease management focuses primarily on lifestyle modification, as there are currently no licensed pharmacological treatments specifically for NAFLD in the UK. The approach, as outlined in NICE NG49, includes:

• Weight loss: A 7–10% reduction in body weight can significantly improve liver fat content, inflammation, and fibrosis

• Dietary modification: Mediterranean-style diet, reduced intake of refined carbohydrates, saturated fats, and sugar-sweetened beverages

• Physical activity: At least 150 minutes of moderate-intensity exercise weekly, adapted to respiratory capacity. Supported physical activity programmes and respiratory physiotherapy or breathing techniques may help patients with asthma to increase activity levels safely.

• Management of metabolic risk factors: Optimising control of type 2 diabetes, hypertension, and dyslipidaemia

Assessment of liver fibrosis is an important component of NAFLD management. NICE NG49 recommends using the Enhanced Liver Fibrosis (ELF) test to assess adults for advanced fibrosis. Many UK primary care pathways also use non-invasive risk scores such as FIB-4 or the NAFLD Fibrosis Score (NFS) as first-line tools, with onward referral for transient elastography or ELF testing as appropriate. It is important to note that liver ultrasound has limited sensitivity for detecting early steatosis, and normal liver function tests do not exclude NAFLD. Assessment should be risk-based, following local guidance and NICE recommendations.

Integrated care strategies should include:

• Multidisciplinary team involvement: Coordination between respiratory specialists, hepatologists, dietitians, and primary care

• Medication review: Regular assessment of all medications for potential metabolic effects and interactions

• Monitoring: Periodic liver function tests and non-invasive liver fibrosis assessment as per local pathways and NICE NG49

• Referral thresholds: Consider hepatology referral when advanced fibrosis is suspected (e.g., raised ELF score per NICE NG49 thresholds) or if there are features of decompensated liver disease

• Cardiovascular risk assessment: Both conditions increase cardiovascular risk, warranting comprehensive risk management

Weight management is particularly crucial, as it benefits both conditions. However, exercise programmes must be tailored to respiratory capacity, with gradual progression as asthma control improves. Patients should be empowered to take an active role in their care, with clear education about both conditions and how lifestyle modifications can improve outcomes for both simultaneously.

References:

• NICE NG80: Asthma: diagnosis, monitoring and chronic asthma management

• NICE NG49: Non-alcoholic fatty liver disease: assessment and management

• British Society of Gastroenterology/British Association for the Study of the Liver: UK pathways for abnormal liver function tests and NAFLD

When to Seek Medical Advice for Asthma and Liver Concerns

Recognising when to seek medical attention is crucial for preventing complications and ensuring optimal management of both asthma and liver health. Patients should be aware of specific warning signs that warrant prompt medical review.

For asthma-related concerns, contact your GP or asthma nurse if:

• Your symptoms are worsening or occurring more frequently (more than three times weekly)

• You're using your reliever inhaler more than three times per week

• Symptoms are disturbing your sleep or limiting daily activities

• Your peak flow readings are declining or becoming more variable

• You've needed oral corticosteroids more than twice in the past year

Seek urgent medical attention (call 999 or go to A&E) if you experience:

• Severe breathlessness or inability to complete sentences

• Blue lips or fingernails

• Exhaustion, confusion, or collapse

• Peak flow less than 50% of your best

• No improvement after using your reliever inhaler

During an asthma attack: Take 10 puffs of your reliever inhaler (one puff at a time) using a spacer if available. If symptoms do not improve, repeat and call 999 immediately.

For liver-related concerns, consult your GP if you notice:

• Persistent fatigue or unexplained weakness

• Discomfort or pain in the upper right abdomen

• Unexplained weight loss or loss of appetite

• Easy bruising or bleeding

• Swelling of the abdomen or ankles

• Itching of the skin

Seek urgent same-day medical assessment if you develop:

• Yellowing of the skin or eyes (jaundice)

• Dark urine or pale stools

• Confusion or altered mental state

• Vomiting blood or passing black, tarry stools

These may indicate serious liver complications requiring immediate evaluation.

Routine monitoring is advisable if you:

• Have been diagnosed with either asthma or fatty liver disease

• Require frequent courses of oral corticosteroids

• Have risk factors for metabolic syndrome (obesity, type 2 diabetes, high blood pressure, high cholesterol)

• Have a family history of liver disease

• Take multiple medications that may affect liver function

Regular health checks should include:

• Annual asthma reviews with peak flow and inhaler technique assessment

• Risk-based assessment for NAFLD if you have obesity, type 2 diabetes, or metabolic syndrome, using non-invasive fibrosis tests (such as FIB-4, NFS, or ELF) as recommended by your GP

• Body mass index (BMI) and waist circumference measurements

• Blood pressure and lipid profile monitoring

• HbA1c testing if at risk of diabetes

Your GP can arrange appropriate investigations, including blood tests, non-invasive fibrosis assessment, or referral to specialist services if needed. It is important to understand that liver ultrasound may miss early fatty liver changes and that normal liver function tests do not exclude NAFLD. Early identification and management of both conditions can prevent progression and improve long-term outcomes.

Don't hesitate to discuss any concerns about your medications or symptoms with your healthcare team—open communication is essential for effective, personalised care. If you experience any suspected side effects from your medicines, report them via the MHRA Yellow Card scheme at https://yellowcard.mhra.gov.uk.

References:

• NHS: Asthma attack – what to do

• NHS: Non-alcoholic fatty liver disease (NAFLD) – symptoms and diagnosis

• British Liver Trust: Patient information on liver symptoms

• MHRA Yellow Card Scheme

Frequently Asked Questions