Liver function tests are simple blood tests that give valuable insight into how well your liver is working. In the UK, these tests are commonly used to check for liver damage, infections, or conditions such as fatty liver disease and hepatitis. Whether you’re feeling unwell, taking long-term medication, or simply having a routine health check, liver function tests can help detect problems early before symptoms appear. In this guide, we explain what liver function tests measure, when your GP may recommend them, and why keeping an eye on your liver health is essential for your overall wellbeing.
Liver Function Tests Explained: When and Why You Need One
We often think of our heart as the engine and our brain as the computer, but if we’re talking about the body’s ultimate multitasker, the liver takes the crown. Tucked away on your right side, just under your ribs, this three-pound powerhouse is working 24/7 to keep you alive. Yet, despite its critical role, we rarely give it a second thought until something goes wrong. In the UK, liver disease is one of the few major causes of premature death that is actually on the rise. Because the liver is a “silent” organ—meaning it doesn’t usually complain until it’s under significant stress—Liver Function Tests (LFTs) are one of the most vital tools in your GP’s diagnostic kit. Whether you’re feeling a bit “off” or just heading in for a routine MOT, understanding these tests is the first step toward taking charge of your long-term wellbeing.
What Are Liver Function Tests?
If you’ve ever had a “full blood count” at your local surgery, you might assume your liver was checked then. However, liver function tests (LFTs) are a specific group of blood tests designed to measure various proteins, enzymes, and substances produced by the liver.
Think of an LFT as a “chemical snapshot”. Rather than looking at the liver’s physical shape (which would require an ultrasound), these tests look at how well the liver is actually performing its duties. If the liver cells are damaged or inflamed, they “leak” certain enzymes into your bloodstream. By measuring these levels, doctors can determine if your liver is struggling, even if you feel perfectly fine.
What Do Liver Function Tests Measure?
When you get your results back on the NHS app or over the phone, you’ll see a list of acronyms that can look a bit like alphabet soup. Let’s break down the most common markers:
ALT and AST (The “Leakage” Markers)
- ALT (Alanine Aminotransferase): This is found mainly in the liver. When liver cells are damaged, ALT is released into the blood. It’s often the most sensitive indicator of liver inflammation.
- AST (Aspartate Aminotransferase): Similar to ALT, but also found in the heart and muscles. High levels usually point toward liver damage, especially when seen alongside a high ALT.
ALP and GGT (The “Flow” Markers)
- ALP (Alkaline Phosphatase): This enzyme is found in the liver and bones. If your bile ducts (the tubes that carry bile out of the liver) are blocked or inflamed, ALP levels usually spike.
- GGT (Gamma-Glutamyl Transferase): This is a very sensitive marker. It often rises if the bile ducts are damaged or if you’ve been drinking more alcohol than the liver can handle.
Bilirubin and Albumin (The “Function” Markers)
- Bilirubin: This is a waste product from the breakdown of old red blood cells. A healthy liver processes it and sends it out in bile. If levels are high, it can cause jaundice (yellowing of the skin and eyes).
- Albumin: This is a protein made by the liver. If your albumin levels are low, it might suggest the liver hasn’t been functioning at full capacity for some time, as it’s failing to produce enough of this essential protein.
When Do You Need a Liver Function Test?
Your GP won’t usually order an LFT without a reason, but those reasons are more common than you might think. You might be asked to provide a sample if you are experiencing:
- Persistent Fatigue: We all get tired, but unexplained, bone-deep exhaustion can sometimes be a sign of liver stress.
- Nausea and Loss of Appetite: If you’re feeling sick or losing weight without trying, the liver might be the culprit.
- Abdominal Pain: Specifically discomfort or swelling in the upper right side of your tummy.
- Jaundice: The most obvious sign—if the whites of your eyes look yellow, see a doctor immediately.
- Dark Urine or Pale Stools: Changes in your “bathroom habits” can indicate that bilirubin isn’t being processed correctly.
Monitoring Medication
In the UK, millions of people take statins for cholesterol or long-term painkillers like methotrexate. These medications are processed through the liver, so your doctor will likely want an annual LFT to ensure your liver is coping well with the treatment.
Who Should Consider Having an LFT?
Even if you feel 100% healthy, certain “risk factors” mean a proactive liver check is a smart move.
- High Alcohol Intake: If you regularly exceed the NHS guideline of 14 units a week (about 6 pints of average-strength beer or 6 medium glasses of wine), your liver is working overtime.
- Obesity and Type 2 Diabetes: Non-Alcoholic Fatty Liver Disease (NAFLD) is becoming incredibly common in the UK. Excess fat can build up in the liver, causing inflammation similar to heavy drinking.
- Family History: Some liver conditions, like haemochromatosis (where the body stores too much iron), are genetic.
- Viral Hepatitis Risk: If you’ve travelled to certain areas, had tattoos in unregulated parlours, or had unprotected sex, a check for Hepatitis B or C is often bundled with an LFT.
How Is a Liver Function Test Performed?
The process is straightforward and identical to any other blood test. You’ll likely head to your GP surgery or a local hospital phlebotomy clinic.
- The Procedure: A healthcare professional will wrap a tourniquet around your arm, find a vein, and take a small vial of blood. It usually takes less than two minutes.
- Fasting: For a standard LFT, you often don’t need to fast. However, if your doctor is also checking your cholesterol or blood sugar (glucose), they might ask you not to eat or drink anything (except water) for 8–12 hours beforehand. Always check your appointment letter!
- Aftercare: You might get a tiny bruise, but you can go straight back to work or head home for a cuppa.
Understanding Your Results
When the results land, remember: one “abnormal” number does not automatically mean liver disease.
- Normal Results: Your levels fall within the “reference range” used by the lab.
- Slightly Elevated: This is very common. It could be due to a recent bout of flu, a heavy night of drinking a few days prior, or even intense exercise.
- Significantly Elevated: This usually triggers a follow-up. Your GP might suggest an ultrasound scan to look at the liver’s structure or a “FibroScan” (a non-invasive test that measures liver stiffness/scarring).
It is important to look at the trends. A single high reading is less concerning than a level that continues to rise over several months.
How to Book a Liver Function Test in the UK
The NHS Route
If you have symptoms or a chronic condition, your LFT is free on the NHS. You’ll need to book a consultation with your GP first to discuss your concerns. Once requested, you can usually get the blood test done within a few days. Results typically take 3–7 days to reach your GP.
Private Options
If you want a check-up for peace of mind or don’t want to wait for a GP appointment, many private clinics in London and across the UK offer same-day blood tests. Providers like Spire, Nuffield Health, or even high-street services like Superdrug or Boots (via private partners) offer “Wellman” or “Wellwoman” screens that include LFTs. These can cost anywhere from £50 to £150 depending on the depth of the panel.
How Often Should You Have a Liver Function Test?
For the average healthy adult with a low-risk lifestyle, a liver test isn’t a monthly requirement. However:
- Annually: If you are on long-term medication (like statins) or have managed Type 2 diabetes.
- Every 3–6 Months: If you are being treated for an active liver condition like hepatitis or cirrhosis.
- Ad hoc: Whenever you notice new, concerning symptoms.
The goal isn’t to obsess over the numbers but to establish a “baseline” so your doctor knows what is normal for you.
Looking After Your Liver Health
While LFTs are great for detection, prevention is much better. Living in a city like London, with its vibrant food scene and “after-work drink” culture, can make it tough, but small changes matter:
- Watch the Units: Stick to the 14-unit limit and try to have at least three “dry days” a week to give your liver time to repair.
- Eat the Rainbow: A diet high in fibre and low in processed sugars helps prevent fatty liver disease.
- Stay Hydrated: Water is the liver’s best friend; it helps the organ filter toxins more efficiently.
- Get Your Jab: If you’re at higher risk (due to travel or work), ensure you’re vaccinated against Hepatitis A and B.
Expert Tip: If you’re overweight, losing even 5-10% of your body weight can significantly reduce liver fat and improve your LFT scores.
Conclusion
The liver is incredibly resilient; it is the only organ in the human body that can actually regenerate itself. But even the strongest engine needs maintenance. Liver function tests are not something to fear—they are a window into your internal health, providing you with the information needed to make better lifestyle choices.
If you’re worried about your alcohol intake, struggling with weight, or just feeling more tired than usual, don’t wait for a “clear sign” like jaundice. A simple blood test could be the most important appointment you book this year. Speak to your GP or book at Health Screening Clinic, get the facts, and give your liver the credit (and the care) it deserves.
Would you like me to create a simple checklist of questions you can take to your GP when discussing your liver health?
