What does high creatinine mean?

You have a lab report in your hand, and next to creatinine there is an H, an asterisk, or a number printed in bold. This page explains what that flag means, what it can tell you, and just as importantly, what it cannot tell you on its own.

What "high" means on a lab report

Every lab compares your result with a reference range. This is the range of values found in most healthy people tested with that lab's method. If your result is above the top of that range, the lab flags it as high.

Reference ranges for creatinine are not the same everywhere. They vary between labs and methods, and they usually differ for men and women because of differences in muscle mass. Some labs also adjust for age. So always read your result against the range printed on your own report, and check the unit. Most Kenyan labs report creatinine in µmol/L, while some use mg/dL, and the numbers look very different.

A result just above the range and a result many times above it are both flagged "H", but they mean very different things. Your clinician will look at how far above the range it is, as well as the other information below.

What a high result can tell you

Creatinine is a waste product made by muscles and cleared by the kidneys. If the kidneys filter less blood, creatinine tends to build up. So a high result may be a sign that kidney filtering is lower than expected for you, either for a short time or for longer.

That is why a high result is worth discussing with a clinician. It is a reason to look more closely, not a conclusion.

What a high result cannot tell you on its own

• It cannot tell you the cause. Dehydration, a big meat meal, heavy exercise, high muscle mass, some medicines and lab differences can all push creatinine up. So can kidney conditions. See causes of high creatinine.
• It cannot tell you whether the change is new or long-standing. Only comparing with earlier results, or repeating the test, can show that.
• It cannot diagnose chronic kidney disease. Under the KDIGO 2024 guideline, CKD is assessed using eGFR and urine albumin together, and the changes must be present for more than 3 months.
• It cannot show early damage that has not yet affected filtering. Protein in the urine can be the first sign, even with a normal creatinine.

Why eGFR matters more than the creatinine number

Clinicians turn your creatinine into an estimated glomerular filtration rate (eGFR). This uses a validated equation, such as CKD-EPI, that combines creatinine with your age and sex. The result, in mL/min/1.73m², is an estimate of how much blood your kidneys filter each minute. KDIGO recommends using eGFR rather than creatinine alone to judge kidney function.

This matters because the same creatinine can mean different things for different people. For example, a result that is only slightly high in a young, muscular man may correspond to a normal eGFR. A result inside the reference range in an older, slim woman may correspond to a reduced eGFR. The equation takes some of this into account, though not all of it, which is why clinicians also look at the whole person.

Read more in eGFR explained.

How a clinician usually interprets a high result

1. Checks for anything urgent, such as signs of acute kidney injury or very abnormal potassium.
2. Compares with any earlier results, to see if the level is new, rising or stable.
3. Reviews your circumstances: recent illness, hydration, exercise, diet, supplements and all your medicines.
4. Repeats the test, timed according to the situation.
5. Adds a urine ACR, and often a urinalysis, to look for kidney damage.
6. Looks for underlying conditions, especially diabetes and high blood pressure.

Only after this does a clinician say whether kidney function is reduced, whether it looks short-term or long-term, and what follow-up is needed.

What about a "normal" creatinine?

A normal creatinine is reassuring, but it does not always rule out a kidney problem. People with low muscle mass can have a normal-looking creatinine with reduced filtering, and albuminuria can be present with any creatinine level. If you have diabetes, high blood pressure or a family history of kidney disease, ask whether you also need a urine ACR.

Frequently asked questions

Is a slightly high creatinine something to worry about?

A result slightly above the range is common and often has a simple explanation, such as dehydration or high muscle mass. It is still worth discussing with a clinician, who may repeat the test and check eGFR and a urine ACR.

Can high creatinine go back to normal?

Yes, it often can. When the cause is short-term, such as dehydration, a medicine effect or a recent illness, creatinine may return to your usual level. When there is long-term kidney damage, creatinine may stay raised. Repeat testing over time shows which is the case.

Why do men and women have different creatinine ranges?

On average, men have more muscle mass than women, so they make more creatinine. That is why many labs print separate ranges, and why eGFR equations include sex.

This page explains what a test or condition involves. It is not a diagnosis and does not replace advice from a doctor who knows your history. Your results should be interpreted together with your symptoms, other tests and a clinical assessment. Medical disclaimer.