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

Creatinine is a waste product made by your muscles and cleared by your kidneys. Its level in the blood — reported on lab work as serum creatinine — is the most common marker of kidney function, because it is the number your lab feeds into the estimated glomerular filtration rate (eGFR), which estimates how fast your kidneys filter blood. A high creatinine result is alarming to see, but it does not always mean kidney disease. This guide explains what creatinine is, normal creatinine levels in mg/dL, what a high or low creatinine means, and — most importantly — how to read the eGFR, which is what clinicians actually act on. Creatinine is normally reported next to BUN, its partner kidney marker.

Key takeaways

• Creatinine comes from the breakdown of creatine in muscle; the kidneys filter it out. Its blood level therefore tracks kidney filtration.¹
• Typical U.S. reference values: about 0.7–1.3 mg/dL for men and 0.5–0.95 mg/dL for women — but sources disagree on the exact cutoffs, and the range depends on muscle mass and your lab's method.²³
• What matters clinically is the eGFR, now calculated in the U.S. with the race-free CKD-EPI 2021 equation: 90 or above is normal; below 60 for more than 3 months defines chronic kidney disease.⁴⁵⁶
• A high creatinine can come from the kidneys (acute or chronic injury, dehydration) but also from high muscle mass, a meat-heavy meal, creatine supplements, or medications that block creatinine secretion without any real drop in filtration.⁷³
• A low creatinine is usually benign — low muscle mass, pregnancy, malnutrition, or advanced liver disease.¹
• High creatinine is not a cancer marker. It speaks about your kidneys and your muscles, not about a tumor.

What is creatinine?

Creatine is a molecule that supplies quick energy to muscle. As it breaks down, it produces creatinine, a waste product that the blood carries to the kidneys, which excrete it in urine. Because this production is fairly constant — it is proportional to your muscle mass — and because the kidneys filter it continuously, the blood concentration of creatinine is a good mirror of filtration function: if the kidneys filter less well, creatinine accumulates and rises.³

That is exactly why nobody stops at the raw number. Your lab uses the creatinine result, together with your age and sex, to compute an estimated glomerular filtration rate (eGFR) in mL/min/1.73 m². The eGFR is far more informative than creatinine alone, and it is interpreted alongside albuminuria (urine albumin) as part of a kidney work-up.⁸⁹

Creatinine is one important caveat away from being a perfect marker: creatinine is not only filtered, it is also secreted by the kidney tubules. That secretion means creatinine-based clearance overestimates true GFR by roughly 10% to 20%.³

Blood creatinine or urine creatinine? This guide covers creatinine in the blood (serum creatinine). Urine creatinine serves a different purpose — validating a urine collection or forming ratios such as the urine albumin-to-creatinine ratio (uACR). It is not interpreted the same way.

Creatinine is almost never ordered by itself. It arrives bundled into a basic metabolic panel (BMP) or a comprehensive metabolic panel (CMP) — routine panels that also report glucose, electrolytes, calcium, and BUN.¹⁰¹¹ Your primary care provider (PCP) typically orders one at a checkup or when investigating symptoms. These panels are standard and widely covered by insurance; if results point to kidney disease, your PCP may refer you to a nephrologist.

Why creatinine is measured

Clinicians check creatinine to:¹

• assess kidney function, at a routine checkup or to follow known kidney disease;
• monitor conditions that put kidneys at risk: diabetes, high blood pressure, older age, certain medications;
• before or during treatment with drugs cleared by the kidneys (to adjust dosing), or before an imaging study with contrast dye;
• work up symptoms that could suggest kidney involvement.

This matters at scale. Chronic kidney disease (CKD) affects more than 1 in 7 U.S. adults — an estimated 35.5 million Americans — and as many as 9 in 10 adults who have CKD are not aware they have it. About 1 in 3 people with diabetes and 1 in 5 people with high blood pressure have kidney disease.¹² A creatinine on a routine panel is often the first hint.

Normal creatinine levels

Below are typical adult reference values. They depend on sex, muscle mass, and your laboratory's method — always compare your number to the range printed on your report.

Creatinine values per the MedlinePlus Medical Encyclopedia.² eGFR values per the National Kidney Foundation and Cleveland Clinic.⁴⁵

Sources genuinely disagree here — and you should know it. MedlinePlus gives 0.7–1.3 mg/dL (men) and 0.5–0.95 mg/dL (women).² StatPearls gives approximately 0.6–1.2 mg/dL (men) and 0.5–1.1 mg/dL (women).³ Cleveland Clinic's basic metabolic panel reference range is 0.58–0.96 mg/dL, with no split by sex.¹⁰ These are not contradictions so much as evidence that there is no single universal cutoff: reference intervals depend on the assay, the population, and the lab. This is precisely why a result 0.05 mg/dL "over the line" means very little on its own, and why the eGFR — not the creatinine — is what gets acted on.

A note on units. The United States reports creatinine in mg/dL. Most of Europe, including France, reports the same molecule in µmol/L (and sometimes mg/L). To convert: µmol/L ÷ 88.4 = mg/dL, and mg/dL × 88.4 = µmol/L. So a European result of 106 µmol/L is 1.2 mg/dL — the same value in different clothing. Note also that a very muscular person can have a higher creatinine with perfectly healthy kidneys, while an older or frail person with little muscle can show a "normal" creatinine while their eGFR is already reduced. That asymmetry is the whole argument for using eGFR.¹³

eGFR: the number that actually matters

If you take one thing from this guide, take this: creatinine alone is misleading, and eGFR is the fix.

The estimated glomerular filtration rate converts your creatinine into an estimate of how many milliliters of blood your kidneys clear per minute, standardized to a body surface area of 1.73 m². It is reported automatically on most U.S. lab panels alongside the creatinine.

eGFR stages, per the National Kidney Foundation:⁴

Two clarifications that trip people up. First, eGFR declines with age even without kidney disease: the NKF gives average values of 116 at ages 20–29, 107 at 30–39, 99 at 40–49, 93 at 50–59, 85 at 60–69, and 75 at 70+.⁴ A 72-year-old with an eGFR of 78 is not automatically ill. Second, a diagnosis of chronic kidney disease requires the eGFR to stay below 60 for three months — a single low reading is not a diagnosis. You can also have CKD with an eGFR above 60 if there are other signs of kidney damage, such as albuminuria.⁵¹⁴

The race-free equation: what changed in 2021

This is the most consequential recent change in kidney testing, and it is worth understanding.

Older eGFR equations included a race coefficient that mechanically raised the estimated GFR for patients identified as Black — a practice with no defensible biological basis that could delay recognition of kidney disease and access to transplant waitlists. In 2021, the National Kidney Foundation–American Society of Nephrology (NKF-ASN) Task Force on Reassessing the Inclusion of Race in Diagnosing Kidney Disease recommended abandoning it.⁶ The same year, a new CKD-EPI 2021 equation was published that estimates GFR from creatinine without race.¹⁵

U.S. practice has followed. The NIDDK states that it "supports the National Kidney Foundation–American Society of Nephrology Task Force's recommendation to calculate eGFR using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations that do not include a race coefficient," specifically the 2021 CKD-EPI creatinine equation, the 2021 CKD-EPI creatinine-cystatin C equation, and the 2012 CKD-EPI cystatin C equation.⁸ StatPearls reflects the same standard.³

If your report is a few years old, or your lab was slow to update, it may still carry a race-based estimate. Ask.

Beyond creatinine: cystatin C

Creatinine has a structural limitation: it depends on muscle mass.¹³ When a precise GFR is needed — at the extremes of body composition, in frailty, before dosing a narrow-margin drug — clinicians can add cystatin C, a filtration marker much less dependent on muscle. The NIDDK is explicit: "Using both creatinine and cystatin C to estimate GFR is preferred and is more accurate than using serum creatinine alone."⁸¹⁵¹⁶

What a high creatinine means

A high creatinine (and the lower eGFR that comes with it) means the kidneys are filtering less well — or that something else has changed production or secretion. The main causes:⁷¹⁷²

• Chronic kidney disease — driven by diabetes, high blood pressure, and age — which raises creatinine slowly, over years;¹²
• Acute kidney injury (AKI) — from dehydration, severe infection, low blood flow, nephrotoxic drugs — which raises it fast, over hours to days;¹⁷
• Dehydration, the single most common benign explanation for a modestly high result;²
• High muscle mass, a recent red-meat meal, or creatine supplements, all of which raise creatinine without any kidney injury. Eating red meat can raise serum creatinine by roughly 30%;³¹⁸
• Rhabdomyolysis — massive muscle breakdown from crush injury, extreme exertion, or certain drugs — which floods the blood with muscle contents. It is "a major cause of AKI," with the risk of AKI estimated between 10% and 50% when CPK is greater than 1000 U/L;¹⁹
• Urinary obstruction — a blockage downstream (stones, an enlarged prostate, a tumor) backs pressure up into the kidney;²
• Medications that block tubular secretion — notably trimethoprim (as in trimethoprim–sulfamethoxazole) and cimetidine. These raise measured creatinine without any real fall in GFR — a "pseudo-elevation." Trimethoprim–sulfamethoxazole can increase serum creatinine by about 15% to 22%.³²⁰

When should you worry? Not because of an isolated number. What counts is the eGFR, its trajectory (stable, or deteriorating?), your albuminuria, and your context. A creatinine slightly over the line, stable for years, in a weightlifter, is a different animal from a value that climbed 40% in a week, or one paired with protein in the urine. A rapid rise or a low eGFR warrants medical attention — but not panic. Kidney numbers are read calmly, over time, in series.

Note also that creatinine is a late marker: about 50% of kidney function must be lost before serum creatinine rises detectably.³ That is a reason to take a genuinely abnormal result seriously — and a reason not to read too much into small wobbles inside the reference range.

Does high creatinine mean cancer? No. Creatinine reflects kidney filtration and muscle mass, not tumor activity. It is not a tumor marker. Some cancers and some cancer treatments can affect the kidneys, but that is not what a high creatinine on a routine panel is announcing. Only your physician decides which further tests are warranted.

What a low creatinine means

A low creatinine gets far less attention than a high one — including from most sites covering this topic — but it is a common result and a common question. It is usually not a cause for concern, and MedlinePlus notes that "low levels of blood creatinine aren't common."¹ The explanations that matter:

• Low muscle mass. This is by far the leading cause. Creatinine is downstream of muscle: a slight build, advanced age, sarcopenia, prolonged bed rest, or an amputation all mean less creatine to break down and therefore less creatinine to measure.³¹³ The number is telling you about your muscles, not your kidneys.
• Pregnancy. Blood volume expands and GFR rises in pregnancy, so creatinine normally runs lower. This is expected physiology, not a problem.³
• Malnutrition or a low-protein diet. Undernutrition, an eating disorder, a deliberately low-protein or plant-forward diet, or starvation all reduce creatinine.³¹³
• Advanced liver disease. The liver is where creatine is synthesized, so serious liver disease can lower creatinine — and MedlinePlus explicitly lists "serious liver disease" among the causes of a low result.¹
• Overhydration, which dilutes the measured concentration.

Here is the clinically important trap: a low creatinine can mask reduced kidney function. Someone with very little muscle can produce so little creatinine that the number lands comfortably in the reference range while their true GFR is already impaired.¹³ This is one of the situations where cystatin C earns its keep.¹⁶ A low creatinine rarely needs treatment in itself — but if it reflects malnutrition or muscle loss, that deserves attention.

The BUN/creatinine ratio

Because creatinine sits next to BUN on every basic panel, U.S. labs and clinicians routinely read the BUN/creatinine ratio — your BUN divided by your creatinine, both in mg/dL. It is normally about 10:1 to 20:1.²¹

The ratio is informative because the kidney handles the two molecules differently: creatinine is filtered and essentially not reabsorbed, while urea is partly reabsorbed — and reabsorbed more when the kidney is conserving water.

• Above ~20:1 — points to a prerenal cause: dehydration, blood loss, heart failure, low kidney perfusion. Gastrointestinal bleeding is the classic non-perfusion cause.
• Around 10:1–20:1 with both values rising together — points to intrinsic kidney disease.
• Below ~10:1 — suggests low protein intake, advanced liver disease, rhabdomyolysis (creatinine rises disproportionately), or dialysis.²¹

Two caveats carry over. The 10:1 baseline holds best in moderate to advanced renal failure, and the ratio is useful but imperfect: BUN answers to diet, hydration, and liver function as much as to the kidney. It orients a work-up; it never closes one.²¹⁷

What can affect your creatinine

Many things shift creatinine: muscle mass and sex, diet (red meat), creatine supplements, hydration, medications, age, and pregnancy.³¹³ Tell your clinician about your training, your supplements, and your prescriptions — they change the interpretation.

On creatine specifically: creatine monohydrate, one of the most-used sports supplements in the U.S., raises serum creatinine simply by supplying more substrate. That elevation is not kidney damage. A 2023 narrative review examining the long-standing claim that creatine harms the kidneys concluded the evidence does not support it in healthy people at recommended doses — its title asks whether it is "time for a requiem for creatine supplementation-induced kidney failure."¹⁸ A widely cited review of common creatine questions reaches the same conclusion.²² If your creatinine is high and you take creatine, say so; cystatin C can settle the question if needed.¹⁶

Recent research

According to recent PubMed publications:

• eGFR without race. Since 2021, the CKD-EPI equation has been revised to remove the race coefficient, following the NKF-ASN Task Force recommendation; the creatinine + cystatin C combination remains the most accurate estimate.¹⁵⁶
• Updated benchmarks for kidney disease. The international KDIGO 2024 guideline defines and stages chronic kidney disease on eGFR and albuminuria — the basis of both diagnosis and follow-up.¹⁴ A large individual-participant meta-analysis in JAMA confirms that eGFR and albuminuria together predict adverse outcomes better than either alone.⁹
• Creatinine's limits are now well characterized. Reviews detail how muscle mass, nutrition, tubular secretion, and drugs distort creatinine-based GFR estimates, and when to reach for cystatin C.⁷¹³
• Protecting the kidneys: SGLT2 inhibitors. Major trials (DAPA-CKD, EMPA-KIDNEY) showed that a drug class, the SGLT2 inhibitors, slows the progression of chronic kidney disease, with or without diabetes.²³²⁴ (eGFR decline served as a trial endpoint — e.g. NCT03036150.)²⁵
• Creatine supplementation, reassessed. Recent reviews find no evidence that creatine at recommended doses damages the kidneys in healthy people, while confirming it raises serum creatinine.¹⁸²²

These findings concern monitoring and management; they do not justify self-medication and do not replace your physician's advice.

Get your creatinine interpreted by AI DiagMe

A creatinine is never read alone: its meaning depends on your eGFR, your muscle mass, your albuminuria, your medications, and how it has moved over time. That cross-referencing is what gives the result its real value.

👉 AI DiagMe interprets your lab results — blood, urine, or stool — in plain language, taking your whole profile into account. An informational service that does not provide a diagnosis and complements, never replaces, your physician.

Frequently asked questions

Bottom line

Creatinine is a muscle waste product filtered by the kidneys, and its main job is to feed the eGFR — the real measure of kidney function. Remember the orders of magnitude (men ~0.7–1.3 mg/dL, women ~0.5–0.95 mg/dL, with genuine disagreement between sources and real variation by lab and by muscle), that a high creatinine is not a cancer sign and may come from muscle, meat, creatine, or medication, and that a low creatinine usually points at your muscles rather than your kidneys. It is the eGFR — now calculated race-free — its trend, and your albuminuria that say whether there's a problem, not the number in isolation. No single value is read alone: what matters is the full set of your markers and your profile — which is what AI DiagMe provides, alongside your physician.

Sources

Official sources and peer-reviewed publications (PubMed, ClinicalTrials.gov) used for this guide: