Serum Creatinine: Low, High and Normal Range by Sex

At a Glance

Creatinine is a waste product from the normal breakdown of muscle and from protein in your food. Your kidneys filter it out, so the blood level reflects how much you make and how well they clear it.

Adult intervals differ by sex: Labcorp reports 0.57 to 1.00 mg/dL for women, 0.76 to 1.27 for men. MedlinePlus publishes different figures again.

Kidney disease raises this number rather than lowering it, so a low creatinine points away from the kidneys. Less muscle producing it is one of the explanations NKF lists, along with diet and pregnancy — though NKF notes the effect of any single factor is highly variable, and the result alone does not identify which applies.

A single mildly high result is nonspecific. Cooked meat, creatine supplements, a hard workout and high muscle mass raise it without filtration truly falling. Several medications raise it too, though the mechanism and the significance differ by drug. Dehydration is different again: it raises creatinine by cutting blood flow to the kidneys, so the number reports a real drop in filtering, generally a reversible one.

A markedly high result needs prompt medical review whatever is behind it — and it is a rise from your own recent results, not a high number on its own, that defines acute kidney injury. Seek care the same day if a high creatinine comes with much less urine, swelling, breathlessness or confusion.

Creatinine is also not sensitive to early kidney damage: Quest states that a result inside the reference range does not rule out impaired kidney function — which is what the eGFR is for.

Pregnancy is the exception. Filtration rises by up to 50%, so creatinine falls because it is cleared faster, not because less is made — and standard eGFR equations are not valid in pregnancy. A pregnant result belongs with a maternity team, not with the adult interval or the eGFR.

Reference intervals vary by laboratory and assay. The one printed beside your own result is what it was measured against.

Where your number sits

To convert: mg/dL × 88.4 = µmol/L

What the test measures

Creatinine is what is left when creatine phosphate in muscle is broken down for energy, and it also arrives from dietary protein. The kidneys filter it into the urine, so what remains in blood is a proxy for filtration — provided you know how much muscle is making it.

Labcorp runs it by kinetic Jaffe method and Quest by spectrophotometry, both reporting an eGFR alongside. It sits on the basic and comprehensive metabolic panels and on any renal panel — BMP, CMP, renal profile, U&E in the UK, KFT and RFT in South Asia.

Common phrases seen on lab reports

CREATININE

CREATININE, SERUM

SERUM CREATININE

CREATININE SERPL QN

CREATININE, S

S CREATININE

S.CREATININE

SR CREATININE

SERUM CR

CREATININE SERUM/PLASMA

CREATININE PLASMA (LAB)

CREAT

CREA

SCR

All name the same measurement. CREATININE, U CONC and CREATININE, RANDOM URINE are urine creatinine, a different test.

How to read your result

A result establishes where your number sits, not why. No row is a diagnosis, and the eGFR on the same report is what your clinician will use — except in pregnancy, where the equations are not valid.

If you remember only one thing

Kidney disease raises creatinine; it does not lower it. So a result below your interval is not evidence of a kidney problem. What it is instead — less muscle, a meat-free diet, pregnancy, something else on the list — the number does not say.

The interval is sex-specific too: Labcorp's ceiling is 1.00 mg/dL for women, 1.27 for men.

Two people, same result

Two people both have a creatinine of 1.10 mg/dL.

The first is a woman whose previous three results were 0.68, 0.71 and 0.74. She is now above Labcorp's female ceiling, and the movement is the finding.

The second is a man who lifts heavily, ate steak the night before and trained that morning; his value sits inside Labcorp's male interval.

Same number, nothing in common clinically — which is why creatinine is read with your sex, your previous results and your eGFR.

What this result cannot tell you

Whether your kidney function is normal. A result inside the interval does not rule out reduced filtration, which is why eGFR is reported beside it.

Whether a high result is your kidneys or your lunch. Several things raise it without filtration changing; dehydration raises it by genuinely reducing filtration; the number cannot tell them apart.

How it compares with someone else's. Intervals differ by sex, laboratory and method.

What is happening over time. One creatinine is a snapshot; the direction across results carries more.

Common interpretation mistakes

Reading a low creatinine as a kidney finding. Wrong direction — kidney disease raises it.

Acting on one mildly high value. Check the explanations above, then repeat it rested and hydrated.

Assuming a normal creatinine settles it. It does not — least of all with little muscle, or in pregnancy.

Stopping a prescribed medication over a creatinine result. Several can raise it, and what that means differs by drug. Talk to the prescriber.

Questions your doctor may ask

What did you eat in the day or two before the test — much meat — and how much had you had to drink?

Do you take creatine, and had you exercised hard in the 48 hours before the sample?

What medications are you taking — cimetidine, trimethoprim, fenofibrate, ritonavir, cobicistat or dolutegravir in particular?

Has your weight, diet or activity changed, and are you or could you be pregnant?

What were your previous results, and when?

Read together with

eGFR — calculated from this creatinine with your age and sex, and the figure kidney function is staged from.

Blood Urea Nitrogen and the BUN/Creatinine Ratio — from the same panel, read alongside creatinine when the question is why it rose. The ratio is a pointer, not a decider.

Cystatin C — a filtration marker independent of muscle mass, brought in when creatinine is hard to trust. NKF notes an eGFR from both markers is more accurate than either alone; it is used alongside creatinine or in place of it, depending on the situation.

Albumin/Creatinine Ratio, Random Urine — detects kidney damage a serum creatinine misses. Creatinine, Random Urine is the same analyte in urine, used to normalize other urine measurements.

Clinical pearls

Creatinine production tracks muscle mass, which is why adult intervals are sex-specific and why the same value means different things in different bodies. NKF notes that a low creatinine can make kidney function look better than it is: someone with very little muscle can carry a normal-looking eGFR alongside reduced filtration.

NKF names six medications that can raise measured creatinine and make a creatinine-based eGFR read low: cimetidine, cobicistat, dolutegravir, fenofibrate, ritonavir and trimethoprim. Mechanism and significance are not the same across all six, so which drug it is matters more than the list.

The race-free 2021 CKD-EPI equation for eGFR was developed by Inker and colleagues and is recommended for US adults by the joint NKF and American Society of Nephrology task force on race in kidney diagnosis. In a March 2023 survey, 65.8% of 3,542 US laboratories reported having adopted it, up from 30.3% the year before.

The UK Renal Association's 2019 guideline recommends assessing renal function in pregnancy using serum creatinine, because estimated GFR is not valid in pregnancy: the equations underestimate measured GFR by up to 20%.

Creatine and creatinine are one letter apart and routinely confused. The International Society of Sports Nutrition's review records that creatine supplementation and creatine-containing foods may raise blood and urinary creatinine, that transient increases of this kind are unlikely to reflect decreased kidney function, and that creatine at recommended doses does not damage healthy kidneys.

Clinical Takeaway

Serum creatinine is a muscle-turnover and dietary-protein waste product the kidneys filter out, so the level reflects production as much as clearance. Adult intervals are sex-specific — Labcorp 0.57 to 1.00 mg/dL for women, 0.76 to 1.27 for men; MedlinePlus 0.5 to 0.95 and 0.7 to 1.3 — and the printed interval governs. Kidney disease raises creatinine, so a result below the interval points away from the kidneys; NKF lists low muscle mass, a meat-free diet, pregnancy, amputation or muscle-wasting disease and severe liver disease without ranking them, and MedlinePlus adds malnutrition. A low value inflates calculated eGFR and can mask reduced filtration where muscle is scarce, which is where cystatin C comes in — an eGFR from both markers being more accurate than either alone. Above the interval, meat, creatine, hard exercise and high muscle mass raise creatinine without a true fall in filtration, whereas dehydration raises it by reducing renal perfusion — a real and generally reversible fall. The six medications NKF names belong to neither group: mechanism and significance differ by drug. Beyond all of it sit reduced clearance, obstruction and muscle breakdown; a rise of 0.3 mg/dL in 48 hours, or to 1.5 times baseline in 7 days, meets a KDIGO creatinine criterion for acute kidney injury, which a high but stable value does not. Quest states that a result inside the reference range does not rule out impaired kidney function, and the eGFR — by the race-free 2021 CKD-EPI equation — is what kidney function is staged from. Pregnancy is the exception: the UK Renal Association guideline states eGFR is not valid in pregnancy, where filtration rises and serum creatinine is used instead.

In one sentence

Creatinine is a muscle waste product your kidneys clear, so a low result points away from the kidneys rather than at them, and a high one is read with your eGFR, your previous results and the things that raise it harmlessly.

Bottom line

Your report shows creatinine, a waste product from muscle breakdown and dietary protein that your kidneys filter out. Adult intervals differ by sex — Labcorp reports 0.57 to 1.00 mg/dL for women, 0.76 to 1.27 for men — and other laboratories differ, so read yours against the interval on your own report.

If your result is low, that points away from your kidneys — kidney disease pushes this number up, not down. Less muscle, a meat-free diet and pregnancy all lower it, and none needs fixing. Raise it with a provider if it is new and your diet, weight and activity have not changed, or if your kidneys are being watched and you have little muscle, since a low creatinine flatters the eGFR.

If your result is mildly high, check the ordinary explanations. A large meat meal, a creatine supplement and hard exercise in the previous day or two can raise it without your kidneys being worse; several common medications raise it too, though what that means differs by drug. Dehydration is different — less blood reaching the kidneys means less filtering, a real drop, though one that generally corrects once you rehydrate.

A markedly high result needs prompt attention whatever is behind it — and it is a rise from your own previous results, not a high number on its own, that defines acute kidney injury. Get seen the same day if you are also passing much less urine, swollen, breathless or confused.

Either way, the figure your clinician will use is the eGFR on the same report, which already adjusts for age and sex — except in pregnancy, where the equations are not valid and the reading belongs with a maternity team. Take both numbers to whoever ordered the test, with any previous results.