Creatinineumol/L
Kidney clearance (muscle-mass dependent)
Typical optimal range
59–104 umol/L
Female
A commonly cited optimal range is 59–104 µmol/L, though reference intervals differ between laboratories depending on their equipment and the population they serve, so your result should always be read against the range provided on your own report. These figures are indicative — the range printed on your own lab report is the definitive one for your results.
Kidney function testing and the management of chronic kidney disease in the UK follows NICE guideline NG203 (Chronic kidney disease: assessment and management).
What is Creatinine?
Creatinine is a waste product produced continuously by the breakdown of creatine phosphate in muscle tissue. It passes into the bloodstream and is filtered out by the kidneys, appearing in urine at a fairly steady rate. Because healthy kidneys clear creatinine efficiently, rising levels in the blood can be an early indicator that the kidneys are not filtering as well as they should. Measuring blood creatinine is most useful when combined with age, sex, and ethnicity to calculate the estimated glomerular filtration rate (eGFR), which gives a clearer picture of overall kidney function.
What a high Creatinine means
A creatinine level above the reference range is a signal worth investigating further — it may point to reduced kidney filtration capacity, but it does not on its own confirm kidney disease. Your GP will look at the full picture, particularly your eGFR and any trends over time, before drawing any conclusions.
- Reduced kidney function. When the kidneys' filtering capacity declines — whether acutely from dehydration, infection, or medication, or gradually through conditions such as chronic kidney disease (CKD) — creatinine accumulates in the blood. This is the most clinically important cause of a raised result and the reason repeat testing and eGFR calculation are standard practice.
- High muscle mass or intense exercise. Because creatinine comes from muscle, people with a large muscle mass (including bodybuilders or manual workers) naturally produce more of it and may have consistently higher levels that still reflect perfectly normal kidney function. Similarly, very intense exercise in the days before a blood test can cause a transient rise.
- High dietary meat intake. Eating a large amount of cooked red meat shortly before a blood draw can temporarily raise creatinine, because cooking converts some of the creatine in meat directly into creatinine, which is then absorbed. This is usually a short-lived effect rather than a sign of kidney trouble.
A single mildly raised reading needs context — your GP will consider hydration status, recent strenuous activity, current medications (some drugs affect creatinine independently of kidney function), and whether the rise is new or longstanding before deciding on next steps.
What a low Creatinine means
A creatinine level below the reference range is usually a reflection of lower-than-average muscle mass rather than a problem in its own right, and in most people it is not clinically concerning on its own.
- Low muscle mass. Older adults, people who are less physically active, or those with conditions causing muscle wasting will produce less creatinine, resulting in lower blood levels. This can actually cause eGFR to overestimate true kidney function, which is one reason clinicians sometimes use additional tests such as cystatin C.
- Malnutrition or very low protein intake. Severely restricted dietary intake, particularly of protein, reduces creatinine production. This is most commonly seen in the context of significant illness, eating disorders, or prolonged malnutrition.
Mildly low creatinine is rarely acted on in isolation, but if your GP suspects muscle wasting or nutritional deficiency they may check other markers alongside it.
Should I be worried?
A single creatinine reading outside the reference range, particularly a mild one, rarely tells the full story on its own. Creatinine is highly dependent on muscle mass, hydration, recent diet, and exercise, so context matters enormously. Your GP will typically look at your eGFR alongside creatinine, and — if there is any concern — arrange a repeat test, since a persistent change is far more meaningful than a one-off fluctuation. If your eGFR is also reduced, or if there are other symptoms such as swelling, changes in urination, or fatigue, your GP may wish to investigate further, potentially including a urine albumin-to-creatinine ratio (ACR) test to check for early kidney stress. Most people who receive a mildly abnormal result turn out to have a straightforward explanation, but it is always worth flagging and discussing so the right follow-up can be arranged.
What actually helps
While you cannot directly lower creatinine by lifestyle alone — and a very low creatinine is not a goal — there are evidence-backed habits that support healthy kidney function and help ensure your result accurately reflects your kidney health rather than confounding factors.
- Stay well hydrated. Adequate fluid intake — around 6–8 glasses of water a day, in line with NHS guidance — supports kidney filtration and helps avoid the dehydration-related creatinine rises that can occur around blood tests. Consistently poor hydration over time places extra strain on the kidneys.
- Time your blood test sensibly. If you do strenuous exercise regularly, try to avoid very intense training in the 48 hours before a blood draw. This reduces the chance of a transient exercise-related creatinine rise being misread as a kidney issue.
- Limit very high meat intake before testing. A large portion of cooked red meat on the evening before a blood test can nudge creatinine upward temporarily. Eating a normal, balanced meal rather than an unusually meat-heavy one helps give a more representative reading.
- Maintain a healthy blood pressure. High blood pressure is one of the leading causes of kidney damage over time. Following NHS guidance on salt reduction, physical activity, and maintaining a healthy weight all help protect kidney function in the long term.
A plant-forward, kidney-friendly eating pattern has good supporting evidence for preserving long-term kidney health.
Vegetables and salad
High vegetable intake is associated with lower blood pressure and reduced acid load on the kidneys; plant-based diets are linked to slower progression of kidney disease in large observational studies.
Fruit (especially berries)
Berries and other fruit provide antioxidants and potassium in a balanced form; a diet rich in fruit and vegetables supports cardiovascular health, which is closely intertwined with kidney health.
Wholegrains
Wholegrain foods help maintain a healthy weight and blood sugar, both of which reduce the risk of diabetes-related kidney damage — the most common cause of CKD in the UK.
Oily fish
Omega-3 fatty acids from oily fish (such as salmon, mackerel, and sardines) have anti-inflammatory effects and are associated with modest reductions in blood pressure; the NHS recommends two portions per week.
Legumes and pulses
Replacing some red and processed meat with plant-based protein sources such as lentils and beans reduces the creatinine-raising effect of a very high meat diet and is associated with better kidney outcomes in prospective studies.
Low-fat dairy or fortified plant alternatives
Adequate calcium intake from dairy or fortified alternatives supports bone health without adding excessive protein load, and dairy consumption is not adversely associated with kidney function in people without existing CKD.
Track your own Creatinine
Upload a lab PDF and Better Days trends Creatinine over time, flags it when it drifts, and suggests foods that help.
More in Kidney
Sources & further reading
These are reputable UK health resources for further reading. This page is written to be consistent with their guidance but is not a substitute for them.
For information only — not medical advice, and not individually reviewed by a clinician. Reference ranges vary by lab and individual. Discuss any results with a qualified clinician before making changes.