Liver function
Liver function tests measure a group of enzymes and proteins in the blood — ALT, AST, ALP, GGT, bilirubin and albumin among them. Which of them moved, and by how much relative to the others, is what gets read. Below are the finding patterns we explain.
Value combinations explained
- Abnormal Liver Tests When Everything Else Came Back Normal A negative workup is genuinely useful information: it has excluded the conditions that need specific treatment. What it has not done is establish that nothing is wrong, and the most common situation at this point is metabolic liver disease, which has no positive test and is diagnosed by what remains. The question now shifts from what is causing this to how much damage has accumulated, and that is a different investigation.
- Fatty Liver on a Scan with Normal Liver Enzymes Normal enzymes are reassuring about inflammation and say almost nothing about scarring, which is the thing that determines what happens over the next twenty years. A substantial proportion of people with significant fibrosis have liver blood tests inside their reference ranges. So the right next step is not another liver panel; it is to work out how much scarring is present, using a score calculated from results already taken.
- A Raised ALP and GGT with a Normal ALT Liver tests split into two families. One reports cells leaking, the other reports bile not flowing. ALP and GGT up with ALT untouched is the second family, and it moves the investigation from hepatitis screens toward pictures of the bile ducts.
- A High ALP in a Teenager Alkaline phosphatase comes from bone as well as liver, and growing bone produces a great deal of it. During the growth spurt a teenager's level can sit several times above the adult upper limit and be entirely normal — which is exactly what happens when a laboratory reports a young person's result against an adult range. With a normal GGT and no symptoms, this almost always needs nothing.
- Liver Enzymes That Rose After a Course of Antibiotics The timing is what makes this one hard to spot: the enzymes typically rise days to weeks after the course has already finished, so the antibiotic has been forgotten by the time the blood test is taken. The pattern is usually cholestatic, not the raised ALT most people associate with liver injury, and co-amoxiclav is the drug behind more cases than any other.
- Liver Enzymes That Rose After a Herbal or Gym Supplement Herbal and bodybuilding products are among the leading causes of drug-induced liver injury, and they are systematically under-reported because people do not count them as medicines. If you have been asked what medications you take and answered honestly without mentioning the protein blend, the joint supplement or the green tea capsules, the most likely cause of your result never made it into the conversation.
- Liver Enzymes That Rose After Starting a Statin A mild rise after starting a statin is common, usually settles on its own, and is rarely a reason to stop. Statins have also been withheld for years from people who needed them because of a number that never mattered. The decision belongs with whoever prescribed it, but knowing where the actual threshold sits changes the conversation you have.
- Liver Enzymes in the Hundreds or Thousands Magnitude changes the differential here in a way it does for almost no other blood test. A mildly raised ALT has a long list of undramatic explanations. Enzymes in the thousands have a short list, most of it acute, and paracetamol overdose sits on it with an antidote that works best before any symptoms appear. This is the one liver pattern where reading and acting should not be separated.
- A Raised ALT in Someone Who Is Not Overweight Most raised ALT results are explained by fat in the liver, and most people with fat in the liver carry extra weight. When that explanation is absent, the list normally skipped becomes the list to work through — and it is worth doing properly, because several of the conditions on it are treatable and a few of them are curable if caught before scarring sets in.
- ALT Raised with a Normal AST and Bilirubin An isolated ALT rise with a normal AST, bilirubin and ALP is the most common abnormal liver result on a routine panel. In adults, the most common explanation for this combination is metabolic fat accumulation in the liver. But a medicine or an over-the-counter supplement will produce it too, and so, less typically, will a hard workout in the days before the draw.
- A Raised ALT with a Raised Ferritin A raised ferritin is read as iron overload more often than any other result on a panel, and in this combination that reading is usually wrong. Ferritin is doing two unrelated jobs at once: holding the body's iron reserve, and rising in step with inflammation wherever it occurs. An inflamed liver lifts it without a gram of excess iron being present. Transferrin saturation is the number that tells the two apart, and it is frequently not requested.
- An AST Higher Than the ALT Both enzymes leak from injured liver cells, so they usually rise together and in proportion. When AST pulls ahead, the balance itself becomes the finding. In an adult with a liver problem that pattern points at alcohol more strongly than any other single number on the panel. It also appears when the source is not the liver at all, and a CK settles which.
- A Raised Bilirubin with a Raised ALP and GGT Bile is not getting out. ALP and GGT rise when the ducts are irritated or obstructed, and bilirubin rises once the blockage is complete enough that it backs up into the blood. That sequence makes this a mechanical problem until an ultrasound says otherwise, and two versions of it need seeing today rather than next week.
- A Raised Bilirubin with the Rest of the Liver Panel Normal Bilirubin raised on its own, with the liver enzymes and the blood count normal, is most often Gilbert syndrome: an inherited difference in how quickly the liver processes bilirubin, present in several people out of every hundred, and harmless. The characteristic clue is that the number moves. It goes up when you have fasted, been unwell, slept badly or trained hard, and comes back down when you have not.
- A Raised Bilirubin with a Low Hemoglobin Bilirubin comes from broken-down hemoglobin, so a raised level with a low hemoglobin usually means red cells are being destroyed faster than usual, and not that the liver is struggling. The liver here is working normally and simply has more to process. Gilbert syndrome, which is the right answer when bilirubin is raised on its own, is the wrong answer once the hemoglobin has fallen.
- A Raised GGT on Its Own GGT is the most easily disturbed enzyme on a liver panel and the least specific about why. Raised on its own, with the ALT, ALP and bilirubin all sitting normal, it seldom represents liver disease that needs treating. Alcohol and a long list of ordinary medicines cover most of it. In a fair number of people it simply runs high with nothing behind it at all.
- A Raised AST with the Rest of the Panel Normal AST raised on its own, while ALT and CK both sit in range, is usually coming from neither the liver nor muscle. Two explanations account for most of these and neither needs treating: red cells breaking down, either inside the body or inside the sample tube, and a harmless bound form of the enzyme that the body cannot clear at its usual speed. The second has a name and a test, and finding it ends the investigation for good.
- Liver Enzymes After Weight-Loss Surgery or Rapid Weight Loss Losing weight quickly can make the liver look worse before it looks better, and that transient worsening is expected, not a sign the surgery has gone wrong. Over the following year the liver usually improves substantially, and the improvement is one of the main benefits of the operation. What needs distinguishing from it is a gallstone, because rapid weight loss forms them and they produce a different pattern.
- Liver Enzymes in Someone with Heart Failure In heart failure the liver panel is often reporting on the heart. Blood backing up behind a struggling right side of the heart congests the liver and raises the cholestatic enzymes; a sudden fall in output starves it and sends the transaminases into the thousands. Which pattern appears tells you which problem the heart is having, and treating the heart corrects the liver.
- Liver Enzymes in Pregnancy One number on this panel changes in pregnancy for a reason unconnected to the liver, and the rest do not. The placenta makes its own alkaline phosphatase, so ALP rises substantially through the second and third trimesters and that is expected. A raised ALT is never explained by pregnancy — so the same panel that would be reassuring outside pregnancy is not reassuring inside it.
- Liver Enzymes Still Raised After Stopping Alcohol The timescale people expect and the timescale the liver actually works to are different, and that mismatch causes a great deal of unnecessary discouragement. GGT takes weeks to fall and the MCV takes months, because it depends on red cells being replaced. So enzymes still abnormal at six weeks are behaving normally, and the useful question is whether they are moving in the right direction, not whether they have arrived.
- Liver Enzymes That Go Up and Down Between Tests A normal result does not undo an abnormal one. Three of the conditions worth finding all fluctuate: metabolic liver disease, hepatitis C and autoimmune hepatitis. Each produces normal readings in between the abnormal ones. Treating a normal test as the end of the matter is a systematic way to miss all three, and the pattern across results says more than any single one.
- Low Albumin with a Raised INR and Bilirubin These three do something the transaminases cannot. ALT and AST count cells being damaged; albumin, INR and bilirubin measure whether the liver is still doing its work. All three moving together is the panel describing lost function, and that is a more serious finding than any enzyme level.
- A High FIB-4 Score with Normal Liver Enzymes FIB-4 is not a test you have to ask for. It is a sum done on four numbers you have already had measured, and it estimates something the panel itself cannot show: whether the liver has scarred. Because it uses age and the platelet count as well as the enzymes, it can flag a liver worth looking at in someone whose liver tests have never once been abnormal.
- Normal Liver Enzymes with a Falling Platelet Count Liver enzymes report on cells being injured. A liver that has finished being injured and is now scarred can have entirely normal enzymes, which is why normal liver tests do not mean a healthy liver. The platelet count is often the first number that moves, and it moves quietly, over years, while everything else on the panel looks fine.