A GP’s guide to blood tests for liver health

The liver is an incredible multitasker. This football-sized organ detoxifies your blood, aids digestion, stores energy, and performs over 500 functions to keep you alive and well. However, when something goes awry with the liver, it may not present symptoms straight away. That’s where liver function tests (LFTs) step in as a critical diagnostic tool. In this article, we'll look into the essentials of liver function tests, what they reveal, and when you might need one.

What are the primary liver function tests?

Liver function tests are a panel of blood tests designed to assess various aspects of liver health. Here’s a breakdown of the key components:

1. Alanine Aminotransferase (ALT): Elevated levels of ALT often indicate liver damage, as this enzyme is released when liver cells are injured.
2. Aspartate Aminotransferase (AST): Like ALT, AST can signal liver damage, but it’s also present in muscles and other tissues, so results must be interpreted carefully.
3. Alkaline Phosphatase (ALP): This enzyme is associated with bile ducts. High levels may point to blockages or issues in bile flow.
4. Gamma-Glutamyl Transferase (GGT): Often used to detect bile duct issues or alcohol-related liver damage.
5. Bilirubin: A byproduct of red blood cell breakdown, elevated bilirubin levels may indicate problems in liver function or bile excretion.
6. Albumin and total protein: These tests measure proteins made by the liver, offering clues about overall liver function.

Together, these tests create a snapshot of how well your liver is functioning and whether there are any potential red flags.

 

What blood test shows liver function?

While the liver function test panel is most commonly used, certain situations call for additional tests:

• Prothrombin Time (PT): Assesses the blood’s clotting ability, as clotting factors are produced in the liver.
• Lactate Dehydrogenase (LDH): Elevated levels may suggest liver injury, although it’s less specific.
• Ammonia levels: High ammonia levels could indicate advanced liver disease, such as cirrhosis.

These tests, combined with LFTs, provide a comprehensive view of liver health.

What are the warning signs of a damaged liver?

Your liver rarely causes pain, but it sends subtle signals when under distress. Here are some common warning signs:

• Jaundice: Yellowing of the skin or eyes due to high bilirubin levels.
• Fatigue: Chronic tiredness can be a symptom of liver dysfunction.
• Dark urine and pale stools: Changes in urine and stool colour may indicate bile flow issues.
• Swelling: Fluid buildup in the abdomen (ascites) or legs can be a late-stage sign.
• Unexplained weight loss or appetite changes
• Nausea and vomiting
• Abdominal pain: Particularly in the upper right quadrant.

If you notice any of these symptoms, consult a healthcare provider promptly.

Why would I need liver function tests?

There are several reasons your doctor might recommend LFTs:

1. Routine screening: Especially if you have risk factors like obesity, heavy alcohol use, or a family history of liver disease.
2. Monitoring chronic conditions: Conditions like hepatitis or cirrhosis require regular monitoring.
3. Diagnosing symptoms: LFTs help investigate symptoms like jaundice, fatigue, or unexplained abdominal pain.
4. Medication side effects: Some drugs, like statins or chemotherapy agents, can affect liver health.
5. Checking for infections: Viral infections like hepatitis B and C are diagnosed and monitored through blood tests.

How to prepare for liver function tests?

Preparing for an LFT is usually straightforward, but a little effort ensures accurate results:

• Fasting: Some tests, like triglycerides or bile acids, may require fasting for 8-12 hours. Follow your doctor’s instructions.
• Avoid alcohol: Alcohol can affect liver enzyme levels, so steer clear for at least 24 hours before the test.
• Medication disclosure: Inform your doctor of any medications, supplements, or herbal remedies you’re taking, as these can interfere with results.

Preparation specifics may vary based on the test, so always clarify with your healthcare provider. Also read: How long to fast before a blood test? A guide

What is a normal liver blood test result?

Normal ranges can vary slightly between labs, but here’s a general guideline:

• ALT: 7-56 units per liter (U/L)
• AST: 10-40 U/L
• ALP: 44-147 U/L
• GGT: 9-48 U/L
• Bilirubin (total):1-1.2 milligrams per deciliter (mg/dL)
• Albumin:5-5.0 grams per deciliter (g/dL)

Deviations from these ranges don’t always mean something is wrong, but they warrant further investigation.

What can a liver function test diagnose?

LFTs are versatile and can help diagnose several liver-related conditions, including:

1. Hepatitis (A, B, C): Viral infections causing liver inflammation.
2. Alcohol-related liver disease: Excessive drinking can damage liver cells and impair function.
3. Non-Alcoholic Fatty Liver Disease (NAFLD): Fat accumulation in the liver not caused by alcohol.
4. Cirrhosis: Scarring of the liver due to chronic damage.
5. Bile duct obstruction: Often caused by gallstones or tumours.

When should I consult a doctor?

You should consult a healthcare provider if you:

• Experience any symptoms of liver damage (e.g., jaundice, dark urine, persistent fatigue).
• Have risk factors such as heavy alcohol use, obesity, or a family history of liver disease.
• Take medications that might affect the liver.
• Have been exposed to hepatitis or other liver-affecting viruses.

Early detection is crucial to managing liver issues effectively.

Can online GPs refer for liver function tests?

Yes, many online GP services can assess your symptoms, order liver function tests, and provide referrals for follow-up care. If you’re dealing with minor symptoms or need a routine check, consulting an online GP can be a convenient starting point. Here's how an online doctor can assist via telehealth:

• Instant consultations: Speak with on-demand doctors via secure video or phone consultations, all from the comfort of your home.
• Online prescriptions: Get instant scripts for necessary medications or supplements to support liver health, with the option for online pharmacy delivery at your convenience.
• Medical certificates: Need time off for testing or recovery? Easily obtain a valid online doctor's certificate for work or school.
• Specialist referrals: Receive online referrals for diagnostic blood tests or consultations with specialists, saving time and effort.

Also read: Can I get my pathology referrals online?

Final thoughts

Liver function tests are a window into your liver’s health, helping detect problems early before they escalate into more serious conditions. Whether you’re experiencing symptoms or proactively monitoring your health, LFTs are a powerful tool in your medical toolkit. If you’re unsure whether you need a test, don’t hesitate to consult a GP—whether online or in-person.