Low creatinine: causes and when to worry

A low creatinine usually does not come from your kidneys. More often it means you have little muscle, because of your build or because you lost it. In pregnancy it normally drops.

What low creatinine means

Creatinine comes from your muscles. The less muscle you have, the less you make, and the number drops.

It is usually nothing to worry about. But if you have lost muscle or weight without trying, it is worth finding out why.

What causes low creatinine

Almost all of them have to do with muscle.

• A small build: People who are small and slim have less muscle and lower creatinine. That is normal.
• Losing muscle: With age, with little movement or after a long time in bed.
• Pregnancy: The kidneys filter more, so the number drops. That is normal.
• A diet without meat: People who do not eat meat often have a slightly lower number. It is not a problem.
• Eating too little: A very poor diet, or an eating disorder, makes you lose muscle.
• Muscle diseases: They are rare, but they reduce muscle a lot.

Symptoms

Low creatinine on its own causes no symptoms.

If there are any, they come from the cause: for example weakness and less strength if you have lost muscle.

Low creatinine or low clearance?

They sound alike, but they are almost the opposite. A low creatinine in your blood usually means little muscle. Clearance and eGFR, on the other hand, estimate how well your kidneys filter: if they are low, your kidneys filter less.

If your report shows a low clearance or eGFR, that is the number to show your doctor.

Which tests to read alongside it

These tests help show where it comes from.

What your result means

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

• Below your report’s limit, Women: usually below 0.51, Men: usually below 0.67: Low. It usually means little muscle. On its own it does not show your kidneys are fine. If you have lost weight or strength without trying, talk to your doctor.
• 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.

What to do if it is low

Usually nothing: the cause matters, not the number.

• If you are small and slim and feel well, you do not need to do anything.
• If you have lost muscle, weight training and enough protein help you build it back.
• If you have lost weight without trying, talk to your doctor.
• In pregnancy it is normal: nothing to do.

When to worry

Talk to a doctor if:

• You have lost weight or strength without trying.
• You have felt weak or tired for weeks.
• Your report also shows a low clearance or eGFR.

Frequently asked questions

Does low creatinine mean my kidneys work well? Not necessarily. Mostly it means little muscle. eGFR, which is calculated from creatinine, can also look better than it is when muscle is low. Your doctor can ask for another kidney test, cystatin C, which does not depend on muscle.

Low creatinine in pregnancy: is it normal? Yes. In pregnancy the kidneys filter more and the number drops. If in doubt, ask your obstetrician.

Do vegetarians have lower creatinine? Often, slightly: meat contains creatine, which the body turns into creatinine. It is not a problem.

How often should it be checked again? If you feel well, with your usual checks: Rosa measures it twice a year. If you have lost weight or muscle, follow your doctor’s timing.

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