Causes of high creatinine

A raised creatinine has many possible explanations. Some mean the kidneys are filtering less well. Others have nothing to do with kidney damage. This page sets out the reasons a clinician may consider, so that you can understand the questions you are asked and bring the right information to your appointment.

It is not a checklist for working out the cause yourself. Several factors often overlap, and only a clinician who knows your history and can order follow-up tests can put them together.

Reasons linked to how creatinine is made or measured

These can raise the number in the blood without the kidneys filtering any less.

• High muscle mass. Creatinine comes from muscle, so people with more muscle make more of it. Manual workers, athletes and people who train at the gym often have results at or just above the upper end of the range.
• Recent heavy exercise. Hard training, a long run or very heavy physical work in the day or two before the test can raise creatinine for a short time. Some of this effect is also from mild dehydration.
• A large meat meal. Cooking meat turns some of its creatine into creatinine. A big meal of meat, such as nyama choma or a stew, in the hours before a blood test can push the result up temporarily.
• Creatine supplements. These are sold for muscle building and can raise blood creatinine. Tell your clinician if you use them.
• Medicines that block creatinine release. The kidneys filter creatinine and also actively release a small amount into the urine. Some medicines block that release, so blood creatinine rises a little even though kidney filtering has not changed. Examples include trimethoprim (part of co-trimoxazole, often known as Septrin), cimetidine, and some HIV medicines. A clinician knows which medicines do this and interprets the result accordingly.
• Lab method and sample factors. Labs use different methods to measure creatinine, and small differences between labs are normal. With some methods, substances in the blood, such as high levels of ketones or some medicines, can interfere with the result. A delay in processing a sample can also affect it. This is one reason clinicians compare results carefully and may repeat a test at the same lab.

Reasons linked to reduced blood flow to the kidneys

The kidneys need a good blood supply to filter. When it falls, filtering falls and creatinine rises. This is often reversible if the cause is treated early.

• Dehydration, from not drinking enough, heavy sweating in the Mombasa heat, vomiting, diarrhoea or fever.
• Blood loss or very low blood pressure, for example during a serious illness.
• Heart failure, where the heart pumps less blood to the kidneys.
• Some medicines, especially anti-inflammatory painkillers (NSAIDs) such as ibuprofen and diclofenac. The risk is higher when someone is dehydrated or is also taking water tablets or certain blood pressure medicines. Some blood pressure medicines that protect the kidneys in the long term cause a small, expected rise in creatinine when started, which is why doctors often repeat the blood test soon after starting them.

Reasons linked to the kidneys themselves

• Acute kidney injury (AKI). A sudden drop in kidney function over hours or days. It can follow severe infections (including severe malaria), severe dehydration, some medicines, contrast dye used in some scans, or a blockage. It needs prompt medical care, and many people recover kidney function.
• Chronic kidney disease (CKD). Long-term kidney damage or reduced function lasting more than 3 months. The most common causes worldwide are diabetes and high blood pressure. Others include inflammation of the kidney filters (glomerulonephritis), inherited conditions such as polycystic kidney disease, and some long-term infections. See high creatinine and kidney disease.
• Diabetes. See high creatinine and diabetes.
• High blood pressure. See high creatinine and high blood pressure.
• Herbal or traditional remedies. Some remedies of unknown content can harm the kidneys. Always tell your clinician about everything you take, including remedies bought at a market or online.

Reasons linked to a blockage

If urine cannot drain freely from the kidneys, pressure builds up and filtering falls. Possible causes include an enlarged prostate in men, kidney stones, and growths that press on the urinary tract. A kidney ultrasound is often used to check for this. See kidney ultrasound.

How the reasons compare

How a clinician works out the cause

The first steps are usually simple: a conversation about your recent health, an examination, a review of every medicine you take, and a repeat blood test. A urine ACR and urinalysis look for signs of kidney damage. If eGFR based on creatinine may be misleading, for example in people with very high or very low muscle mass, KDIGO suggests clinicians can measure cystatin C, another blood marker that is not made by muscle. Not every lab offers it.

To help, before a repeat test your clinician may ask you to be well hydrated and to avoid very hard exercise and a large meat meal the day before. Follow any instructions you are given.

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.