Creatinine Blood Test: High, Low, eGFR & Normal Range

Creatinine is produced through normal muscle and dietary creatine turnover. It enters the blood and is removed mainly by kidney filtration, with some tubular secretion. A serum or plasma creatinine test therefore gives useful information about filtration, but it does not directly measure every kidney function or reveal why filtration changed.^{See reference 1,See reference 4,See reference 5}

Production differs between people. Someone with more muscle may generate more creatinine; someone with frailty, muscle loss or an amputation may generate less. A value that is inside the printed interval can therefore coexist with kidney disease, while a mildly high value can sometimes overstate the problem.^{See reference 3,See reference 4,See reference 5}

Serum creatinine is not urine creatinine. Urine creatinine is used in ratios or timed clearance collections and has different units and interpretation. Combining them into one normal range is a category error.^{See reference 4}

A reference interval describes results observed with one laboratory method and reference population. eGFR categories estimate filtration using creatinine plus other variables. CKD diagnosis then combines filtration, markers of kidney damage and chronicity. Those are three different concepts.^{See reference 1,See reference 2,See reference 6}

KDIGO classifies eGFR of 60–89 mL/min/1.73 m² as G2, but G1 or G2 alone is not CKD without other evidence of kidney damage. An eGFR below 60 that persists for at least three months is one CKD criterion. A single new low result could instead be acute, temporary or imprecise and should not be staged from a web chart alone.^{See reference 1}

A rapid creatinine rise can be important before a new steady state is reached. Waiting three months is not the instruction for suspected acute kidney injury; chronicity is the rule for calling disease chronic, not a reason to delay urgent care.^{See reference 1,See reference 9,See reference 10}

To convert serum creatinine from mg/dL to µmol/L, multiply by 88.4. To convert µmol/L to mg/dL, divide by 88.4. For example, 1.00 mg/dL equals 88.4 µmol/L, and 90 µmol/L is about 1.02 mg/dL.^{See reference 2}

The converter works only in this browser and sends no value for interpretation. It cannot calculate eGFR, identify acute kidney injury, diagnose CKD, set a medication dose or apply pregnancy and pediatric equations.^{See reference 1,See reference 2,See reference 7,See reference 8,See reference 9}

A true rise can reflect reduced filtration from acute kidney injury or chronic kidney disease. Possible pathways include dehydration or poor blood flow to the kidneys, infection or inflammation, urinary blockage, severe illness, heart failure and direct kidney injury. The creatinine number does not distinguish these causes by itself.^{See reference 1,See reference 4,See reference 10}

Creatinine can also be higher because more is being produced or measured: greater muscle mass, muscle injury, hard recent exercise, cooked meat, creatine supplements, medicines that reduce tubular secretion, or assay interference. Those factors can explain a discordant result, but they are not a reason to dismiss a rapid rise, urine abnormality or symptoms.^{See reference 1,See reference 3,See reference 4,See reference 5,See reference 11}

Baseline matters. A change from 0.7 to 1.1 mg/dL may still sit inside some printed intervals but represent a substantial individual rise, while a stable value just above an interval may fit a muscular person differently. The trend, eGFR, UACR, urinalysis and clinical context make the result useful.^{See reference 1,See reference 2,See reference 4,See reference 5,See reference 9}

Low serum creatinine is uncommon and usually reflects lower production rather than kidneys that are ‘too efficient.’ Common contexts include low muscle mass from aging, frailty, chronic illness or amputation, as well as malnutrition and severe liver disease.^{See reference 4,See reference 5}

Pregnancy usually lowers creatinine because filtration increases. Standard adult eGFR equations are not validated in pregnancy, so the result needs pregnancy-specific clinical interpretation rather than the general eGFR chart.^{See reference 5,See reference 7,See reference 8}

Low production can make creatinine-based eGFR look higher than true filtration. If frailty, major weight or muscle loss, amputation or a critical treatment decision is present, cystatin C, a combined equation or measured GFR may add useful information.^{See reference 1,See reference 2,See reference 3,See reference 5}

The goal is not to lower creatinine at any cost; it is to identify and address the cause. If dehydration, a cooked-meat meal, strenuous exercise or supplement timing may have affected a stable outpatient result, a clinician may repeat the test under clearer conditions. Do not delay assessment of a rapid rise or serious symptoms while trying home fixes.^{See reference 1,See reference 4,See reference 5,See reference 7,See reference 10}

Do not stop prescribed medicines, NSAIDs, creatine or other supplements solely from this page. Some medicines truly affect kidney function; others change creatinine secretion or measurement. The safe response depends on why you take the product, the size and timing of the change, eGFR, potassium, urine findings and illness context.^{See reference 1,See reference 3,See reference 4,See reference 5,See reference 10}

A 2026 meta-analysis of randomized trials found creatine raised serum creatinine by an average 0.13 mg/dL, while pooled eGFR and urea differences were not statistically significant. Only eight trials contributed eGFR and long-term evidence remains limited. This can explain a measurement shift; it does not prove safety for every person or make kidney monitoring unnecessary.^{See reference 11}

When kidney disease is confirmed, management is cause- and risk-specific. It can include blood-pressure and diabetes care, medication review, albuminuria-guided treatment and avoidance of kidney injury. Generic detoxes, extreme protein restriction or forced overhydration are not evidence-based substitutes for that plan.^{See reference 1}