How to Check Your Liver Function

Some symptoms mean you should skip the research phase and talk to a healthcare provider soon. Testing is often ordered because of exactly these signs, and a provider can decide which tests you need and how quickly.

Symptoms that can point to a liver problem include (1):

• Yellowing of the skin or the whites of the eyes (jaundice)
• Dark urine or pale stool
• Swelling or pain in your belly
• Swelling in your ankles and legs
• Nausea, vomiting, fatigue or a loss of appetite
• Frequent itching

No symptoms? Testing can still make sense if your risk is higher, for example if you have a family history of liver disease, drink heavily, live with obesity or diabetes, or take medicines that can affect the liver (1). That's a great reason to ask about a panel at your next checkup.

The blood test that shows liver function is called a liver function test, or liver panel. It measures several substances your liver makes or clears, all from one small blood sample (1).

Here's what usually shows up on the report. ALT, AST, ALP and GGT are enzymes that are mainly made in the liver, and ALT and AST tend to rise when liver cells are stressed. Bilirubin is a waste product from old red blood cells that your liver clears. Albumin and total protein are proteins made mostly in the liver, so they hint at how well it's keeping up with its day job. Some panels add prothrombin time (PT), which measures how long your blood takes to clot, since the liver makes clotting proteins too.

One important thing to know up front: these tests can show whether your liver is working well and whether it may be stressed, but on their own they usually can't diagnose a specific condition (1). They're a great first look, but your doctor fills in the rest!

For most people, the best way to check liver function is a panel ordered by a provider. A health professional draws blood from a vein in your arm, it takes a few minutes, and the risk is very low (1). Your provider also sees your history and medicines, which matters when it's time to read the results.

So what about checking your liver function at home? There's no reliable way to do it by symptoms alone. What you can buy are at-home collection kits: you prick your finger, collect a small blood sample, and mail it to a lab that runs some of the same markers. They can be convenient if getting to a clinic is tricky, and they're a reasonable way to start a conversation.

There are a few trade-offs to know about, though. Collection technique matters, the marker list is often shorter than a full panel, and a number without context can cause more worry than clarity. The FDA's own guidance is that home tests should help with your health care, not replace regular visits with your provider (3).

Good prep makes your results easier to trust. Your provider will tell you exactly how to prepare, and you'll probably be asked to fast (not eat or drink) for 10 to 12 hours beforehand (1).

A few everyday things can nudge your numbers, so it's worth planning around them:

1. Tell your provider about everything you take, including supplements. Certain medicines and dietary supplements can affect ALT, but don't stop taking anything unless your provider tells you to (4).
2. Ask how long to skip alcohol. Drinking can raise GGT, and your provider may give you specific instructions before testing (5).
3. Go easy on the gym. Intense exercise can affect your ALT levels, so a hard workout right before your test isn't ideal (4).

That first point includes us! If you take The Plug Drink or Pills, put them on the list along with everything else. Herbal blends are exactly the kind of thing your provider wants to know about, and being upfront means your results get read in the right context. We wrote more about how to think about supplements in Let's Discuss: Do You Really Need Supplements?

The actual blood draw is the quickest part of the whole process. A technician cleans a spot on your arm, may wrap a band around it, and draws blood into a small vial. You might feel a little sting, and it's usually over in less than five minutes (1).

Wear short sleeves or something that rolls up easily, bring your medicine and supplement list, and follow your fasting instructions exactly. Once you're done, you can usually eat, drink and take your medicines again as long as you're not feeling lightheaded. Results can come back in a few hours or a few days, depending on the lab (6).

When your report arrives, each value is listed next to a reference range, the span of results considered normal for healthy people. Those ranges come from large groups of people and can differ by lab, age and sex (7). So always compare your number with the range printed on your own report, not one you found online.

Understanding abnormal results is often complicated, which is why MedlinePlus recommends asking your provider to explain them (1). Providers look at patterns across the whole panel rather than one number. And a high result doesn't always mean a liver problem: ALT can be affected by age, sex, weight, medicines, supplements, intense exercise and even where you are in your menstrual cycle (4). A recent illness can cause temporary changes too.

To give you a feel for what your provider is looking at: high ALT and AST can signal that liver cells are under stress, and low total protein can suggest the liver isn't making as much protein as it should (6). When ALP and GGT are both high, the question often shifts to the bile ducts (8). None of these is a diagnosis on its own, which is exactly why the conversation matters.

One test is a snapshot. If something was slightly off, your provider may simply repeat the panel later to see whether it settles back into range (1). If you're being monitored for a medication or an existing condition, you'll likely test on a regular schedule.

In the meantime, the everyday habits that are kind to your liver are the same ones that are kind to the rest of you: drinking less alcohol, moving your body, eating more whole foods and fewer highly processed ones, and keeping an eye on the medicines and products that pass through your system. If you want a head start, our posts on the hidden daily threats to your liver and easy exercises for liver and gut health are good places to begin.

Then show up for the next test with the same prep, so you're comparing apples to apples.