High creatinine: what it means and what to do
Medically Reviewed by Dr. Pedro Yelamo Vera, MD
Licensed Physician No. 484814280 · Official Medical College of Bizkaia (Spain)Last reviewed: 20 October 2026
High or low creatinine explained: common causes, eGFR, when it matters and when to repeat it. Emergencies in Spain: call 112.
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Creatinine is probably the blood-test value that causes the most uncertainty: it rises with the kidney, but also with the gym, with meat and with several medicines. And a single number without context says very little: what the doctor really assesses is the glomerular filtration rate (eGFR) and the trend over time. This guide explains what the value measures, why it can go up — or down — and what usually happens next.
- Creatinine is a muscle waste product; the kidneys clear it from the blood.
- Typical adult ranges in Spain are about 0.7–1.3 mg/dL in men and 0.6–1.1 mg/dL in women.
- The number that guides decisions is the eGFR, printed next to it on the report.
- Gym training, creatine supplements, a meat-heavy meal and dehydration can all raise it temporarily.
- A high creatinine with a low eGFR on two separate tests needs a proper kidney review.
- Very little urine, sudden swelling or confusion: call 112 — do not wait for a video visit.
What it measures and the ranges you will see
Creatinine is a waste product of muscle; the kidneys remove it. Spanish laboratories report it in mg/dL, and nearly every modern report also prints the eGFR (filtrado glomerular estimado), calculated from creatinine together with your age and sex. That is the figure that actually guides decisions, because creatinine alone does not account for how much muscle you have.
Why it can be high without any kidney disease
- A large muscle mass: muscular people and strength athletes start from higher baselines; creatine supplements also raise it.
- Meat or fish in the 24 hours before the blood draw — a temporary bump.
- Dehydration from heat, gastroenteritis or simply not drinking enough — very common in a Spanish summer.
- Medicines: anti-inflammatory painkillers (ibuprofen and similar), some antibiotics, and blood-pressure drugs such as ACE inhibitors can nudge creatinine up without meaning the drug must be stopped; after starting those drugs the level is checked at 7–10 days.
- Recent contrast scans and intense exercise before the draw.
When it does point to a kidney problem
Creatinine starts to rise only after the kidney has lost a meaningful share of its function, which is why a persistently high value or a low eGFR on two separate tests deserves assessment. Speed matters too: a sharp rise over days (severe dehydration, obstruction, infection) is urgent; a slow drift over months is investigated calmly.
Low creatinine: what it means
A somewhat low creatinine usually reflects low muscle mass: older people, very slim people, low-protein diets, or pregnancy. On its own it almost never indicates disease — but in older people the eGFR calculated from it can overestimate kidney function, which is worth mentioning at the appointment.
What usually happens next
- Repeat the test well hydrated, after 24 hours without intense training and without meat the day before, ideally at the same laboratory.
- Review the eGFR, the urine (protein) and the blood pressure — together they define whether the kidney is affected.
- Review medicines: anti-inflammatories, diuretics and supplements are the usual suspects.
Emergencies
Go to an emergency department or call 112 if you are passing very little or no urine, have sudden swelling of the legs or face, trouble breathing, persistent vomiting or confusion. A chronically high value without symptoms is not an emergency — but it is an appointment with your doctor.
High creatinine and no one has explained what it means?
Dr. Pedro Yelamo Vera, a GP licensed in Spain, reviews your report and your eGFR by video, in English or Spanish, and tells you what usually happens next.
Frequently asked questions
What is a normal creatinine level?
Around 0.7–1.3 mg/dL in men and 0.6–1.1 mg/dL in women; each laboratory prints its own range. The eGFR adds the important context.
Can the gym raise creatinine?
Yes. Intense training, greater muscle mass, creatine supplements or a meat-heavy meal the day before the draw all raise it temporarily.
What is the eGFR?
It estimates how much blood the kidneys filter per minute, calculated from creatinine, age and sex. A normal or mildly reduced eGFR without symptoms is usually reassuring.
Is high creatinine the same as kidney disease?
Not always. Dehydration, medicines and muscle mass can raise it too. The eGFR, the urine tests and the trend over time are what define the assessment.
Sources
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This content is written and reviewed by a licensed physician with reference to the following official health authorities.
