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Doctor's Assessment Included

Every result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

Kidney

Creatinine levels: what do they tell you about your kidney function?

Creatinine is a critical kidney marker for athletes. Higher muscle mass, intense training, creatine supplementation, and high-protein diets can all raise creatinine levels, making it essential to interpret results in the context of your training regimen and body composition.

Reference Ranges

Male
umol/l
Low 62 Normal 106 High
Female
umol/l
Low 44 Normal 80 High

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

What It Measures

This test measures the concentration of creatinine in your blood, expressed in micromoles per litre (µmol/L). Creatinine production is relatively constant and depends on your muscle mass — which is why normal values for men (62–106 µmol/L) are higher than for women (44–80 µmol/L).

Kidney function is not assessed on creatinine alone. Together with your age, sex, and ethnicity, creatinine is converted to the eGFR (estimated glomerular filtration rate), which gives a more accurate picture of how much blood your kidneys filter per minute.

A single creatinine measurement is a snapshot. With a borderline value, your doctor may decide to repeat the test after a few weeks, as temporary factors such as dehydration or intense exercise can influence the value.

Why It Matters

Chronic kidney damage often progresses silently and rarely causes symptoms in early stages. Your kidneys can lose up to 50% of their function before you notice anything. Creatinine and eGFR are the standard markers for early detection.

In diabetes and high blood pressure — the two leading causes of chronic kidney damage — periodic creatinine monitoring is part of clinical guidelines. Kidney function monitoring is also recommended during long-term use of NSAIDs (painkillers such as ibuprofen and diclofenac), ACE inhibitors, or certain antibiotics.

An elevated creatinine does not always indicate kidney damage. In people with high muscle mass (strength athletes) or high protein intake, the value can naturally be higher. Conversely, low creatinine in the elderly or in people with little muscle mass can mask reduced kidney function — eGFR is more reliable in those cases.

When to Test

A creatinine test is useful with known risk factors for kidney problems: diabetes, high blood pressure, a family history of kidney disease, or long-term use of medications that can burden the kidneys.

For symptoms such as unexplained swollen ankles, foamy urine, persistent fatigue, or reduced urine output, creatinine can help rule out or confirm kidney problems.

If you are over 50, periodic kidney function monitoring is sensible, especially combined with blood pressure and blood sugar checks. Fasting is not required, but avoid a heavy protein-rich meal or intense strength training just before the blood draw.

Symptoms

Low Levels

A low creatinine level is usually harmless and occurs in people with little muscle mass, the elderly, or those on a low-protein diet. It can also occur during pregnancy due to increased kidney blood flow. There are typically no symptoms associated with low creatinine.

High Levels

An elevated creatinine level can go unnoticed for a long time because the kidneys have significant reserve capacity. With considerable kidney function reduction, symptoms may include fatigue, decreased appetite, nausea, itching, swollen ankles and legs, and changes in urine output (more or less than normal).

With an acutely significantly elevated creatinine — for example from dehydration, urinary obstruction, or a toxic substance — symptoms such as nausea, vomiting, confusion, and severely reduced urine output may occur. This requires immediate medical attention.

Recommendations

Male

If Low

Low creatinine may indicate reduced muscle mass. Consider evaluation if unexpected.

If High

Elevated creatinine may indicate kidney dysfunction. Consult your healthcare provider for kidney function evaluation.

Female

If Low

Low creatinine may indicate reduced muscle mass. Consider evaluation if unexpected.

If High

Elevated creatinine may indicate kidney dysfunction. Consult your healthcare provider for kidney function evaluation.

Lifestyle Tips

Supporting healthy kidney function starts with adequate hydration. Drink water regularly throughout the day — dehydration is a common cause of temporarily elevated creatinine. Excessive drinking is not necessary either and can disrupt electrolyte balance.

Limit the use of NSAIDs (ibuprofen, diclofenac, naproxen) as chronic use can cause kidney damage. Paracetamol at normal doses is safer for the kidneys.

A diet with moderate protein intake supports kidney function. Extremely high protein consumption (above 2 grams per kilogram of body weight) can raise creatinine and burden the kidneys over time, especially in people with already reduced kidney function.

Keep your blood pressure and blood sugar under control — these are the two biggest risk factors for chronic kidney damage.

Frequently Asked Questions

What is a normal creatinine level?
Normal values are 62–106 µmol/L for men and 44–80 µmol/L for women. The difference is due to the difference in muscle mass. In people with high muscle mass, the value can be slightly higher without indicating kidney problems.
What does elevated creatinine mean?
An elevated creatinine level can indicate reduced kidney function, but also dehydration, high protein intake, intense strength training, or medication use. The eGFR (calculated from creatinine) provides a more reliable picture of actual kidney function.
What is the difference between creatinine and eGFR?
Creatinine is the raw blood value. eGFR is calculated from your creatinine together with your age, sex, and ethnicity, and gives a more precise estimate of your kidney function. An eGFR above 90 ml/min is normal; below 60 ml/min indicates reduced kidney function.
Do I need to fast before a creatinine test?
Fasting is not strictly required, but avoid a heavy protein-rich meal or intense strength training just before the blood draw, as both can temporarily raise creatinine.
Can creatine supplementation affect my creatinine level?
Yes, using creatine supplements can raise the creatinine level in your blood. Creatinine is a breakdown product of creatine. If you take creatine, report this to your doctor so the result can be correctly interpreted.
How can I protect my kidney function?
Drink enough water, keep your blood pressure and blood sugar under control, limit NSAID use (ibuprofen, diclofenac), avoid extremely high protein intake, and have your creatinine and eGFR checked periodically if you have risk factors.

Test Products

This marker is included in the following test panels.

Complete Health

360 Health

Broad health panel: hormones, thyroid, vitamins, lipids, liver, kidney, and blood count.

HbA1c (Glycated Hemoglobin) TSH (Thyroid Stimulating Hormone) Triglycerides Urea (BUN) Creatinine eGFR (Estimated Glomerular Filtration Rate) Free T4 (Thyroxine) LDL Cholesterol Liver Function Test (LFT) SHBG (Sex Hormone Binding Globulin) Vitamin B12 Vitamin D (25-OH) Free Testosterone Total Testosterone Free T3 (Triiodothyronine) Ferritin HDL Cholesterol Albumin Complete Blood Count (CBC)
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