High creatinine: what it means and what to do

A high creatinine does not have to mean your kidneys are not working well. More muscle, a creatine supplement, too little water or a hard workout are often behind it. Two tests help tell whether your kidneys are involved: eGFR shows how well they filter, urine albumin whether they let protein through.

What high creatinine means

Creatinine comes from your muscles and your kidneys clear it. It rises when your kidneys filter less, but also when your muscles make more of it.

That is why the number alone is not enough. If your eGFR is above 60 and your urine albumin is normal, your kidneys are usually fine.

What causes high creatinine

The first four usually do not mean kidney disease.

• More muscle: People with a lot of muscle have higher creatinine, with healthy kidneys.
• Creatine supplements: Popular with people who lift weights. They push it up a little without affecting the kidneys.
• Too little water: If you are dehydrated the number rises, and it comes back down once you drink normally again.
• Hard exercise or lots of protein: A hard workout can raise it for a day or two. A very high protein diet keeps it a little higher.
• Some medicines: Some raise it without the kidneys filtering less, others can put strain on the kidneys. Bring your doctor the list of what you take.
• Kidneys that filter less: This comes with age, and more often with diabetes and high blood pressure. It shows in eGFR and urine albumin.

Symptoms

Usually none. Kidneys slow down quietly, and it is often found by chance on a blood test.

Only when they filter much less can tiredness, swollen ankles or less urine than usual appear. Foamy urine can mean protein in the urine, even earlier: tell your doctor.

High creatinine in people who lift weights

This is one of the most common situations. People who train with weights have more muscle and often take creatine, so creatinine rises even with healthy kidneys. And eGFR, which is calculated from creatinine, can look lower than it really is. But below 60 it should still be seen by a doctor.

If in doubt, your doctor can ask for another kidney test, cystatin C, which does not depend on muscle.

Which tests to read alongside it

These tests help show whether your kidneys are involved.

What your result means

The upper end of the scale, in mg/dL.

• Within your report’s limits, Women: usually 0.51 to 0.95, Men: usually 0.67 to 1.17: Normal. Usually fine. Check your eGFR too, which takes your age into account. In the Rosa report you also see whether you are in your optimal range.
• Above your report’s limit, Women: usually above 0.95, Men: usually above 1.17: High. It can come from muscle, creatine or too little water, or from kidneys that filter less. If your eGFR is below 60 or your report flags albumin in your urine, talk to a doctor. Otherwise, repeat the test rested and well hydrated.

How to lower your creatinine

It depends on the cause. Where to start:

• Repeat the test fasting, well hydrated and without hard exercise in the days before.
• If you take creatine, tell your doctor: sometimes it is paused for a few weeks before the test is repeated.
• Drink enough water through the day.
• What to eat: if your kidneys are fine, you do not need a special diet, and fruit and vegetables are good for you. If they filter less, your doctor decides the diet, often with less salt.
• Keep your blood pressure and glucose in check: that protects your kidneys.
• Do not take medicines or supplements without asking your doctor, especially if your eGFR is low.

When to worry

Talk to a doctor if:

• Your eGFR is below 60.
• Your report flags albumin in your urine.
• It stays high when the test is repeated rested.
• It rises from one test to the next.
• Your ankles are swollen.
• You pass much less urine than usual: see a doctor the same day.

With Rosa, an eGFR below 60 or a urine albumin-to-creatinine ratio of 30 mg/g or more is always flagged to a doctor.

Frequently asked questions

Slightly high creatinine: should I worry? Usually not, if your eGFR is above 60 and your urine albumin is normal. Muscle, creatine or too little water are often behind it. Repeat the test rested and well hydrated.

Creatinine at 1.5: is it serious? It depends on age, sex and muscle. In a young, very muscular man it may not be a problem. In a woman of 70, though, it gives an eGFR below 45: her kidneys filter less, and she should see a doctor. That is why eGFR is what counts.

Low eGFR and high creatinine: what does it mean? They usually go together: eGFR is calculated from creatinine, so when creatinine rises, eGFR falls. Below 60, talk to a doctor.

Is high creatinine dangerous? Not by itself: it is a signal. What matters is how well your kidneys filter. If your eGFR stays low for months, your kidneys need a doctor’s care: protecting them early makes a difference.

Can I eat eggs, pasta and fish with high creatinine? If your kidneys are fine, yes: you do not need to cut anything out. If they filter less, your doctor decides what and how much to eat.

How long does it take to bring creatinine down? If the cause is too little water or hard exercise, it comes down within a few days. After stopping creatine it usually takes a few weeks. If your kidneys filter less, the goal is to protect them, with your doctor.

Sources

• KDIGO clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International, 2024. PMID 38490803
• Inker and colleagues, new equations to estimate kidney filtration from creatinine and cystatin C. New England Journal of Medicine, 2021. PMID 34554658
• Groothof and colleagues, creatinine, cystatin C, muscle mass and mortality in two population cohorts. Journal of Cachexia, Sarcopenia and Muscle, 2024. PMID 38898741
• Nair and colleagues, effect of a cooked meat meal on serum creatinine and eGFR. Diabetes Care, 2014. PMID 24062331