Creatinine
A blood test that measures creatinine, a waste product from normal muscle metabolism, to evaluate how well the kidneys are filtering the blood.
Last updated: April 10, 2026
Creatinine is one of the most important markers of kidney health. It is a waste product created when muscles break down a compound called creatine, which is used for energy. Healthy kidneys filter creatinine out of the blood and remove it through urine. When kidney function declines, creatinine builds up in the bloodstream. Normal levels are 0.7–1.3 mg/dL for men and 0.6–1.1 mg/dL for women, though values depend on age, muscle mass, and the specific laboratory.
Why Is Creatinine Tested?
The serum creatinine test is one of the primary tools for assessing kidney function. The kidneys filter about 200 liters of blood every day, removing waste products and excess fluid. When this filtering ability is impaired — whether from disease, dehydration, medication effects, or other causes — creatinine levels in the blood rise.
Creatinine is a standard component of the Comprehensive Metabolic Panel (CMP), which means it is tested as part of routine blood work during annual physicals and hospital admissions. It is also used to calculate the estimated glomerular filtration rate (eGFR), a more precise measurement of kidney function that accounts for age, sex, race, and body size.
A healthcare provider may order creatinine testing to screen for chronic kidney disease, monitor known kidney conditions, check kidney function before starting certain medications (such as metformin or contrast dye for imaging studies), or evaluate symptoms like swelling, fatigue, changes in urination, or unexplained high blood pressure.
Normal Reference Ranges
Reference ranges vary by laboratory, testing method, and individual factors. Always use the ranges on your lab report. The values below are general guidelines for adults.
| Category | Range | Unit |
|---|---|---|
| Adult Men | 0.7 – 1.3 | mg/dL |
| Adult Women | 0.6 – 1.1 | mg/dL |
| Children (ages vary) | 0.2 – 1.0 | mg/dL |
| Adult Men (SI units) | 62 – 115 | μmol/L |
| Adult Women (SI units) | 53 – 97 | μmol/L |
| Status | Creatinine Level |
|---|---|
| Normal | Within reference range for sex and age |
| Borderline / Mildly Elevated | Slightly above the upper limit (e.g., 1.4–1.6 mg/dL in men) |
| High | Significantly above reference range (e.g., >2.0 mg/dL) |
What Does a HIGH Creatinine Level Mean?
Elevated creatinine typically means the kidneys are not filtering waste as efficiently as they should. However, not all high readings indicate kidney disease.
Possible causes of elevated creatinine include:
- Chronic kidney disease (CKD) — a gradual loss of kidney function over months or years
- Acute kidney injury (AKI) — a sudden decrease in kidney function, often from dehydration, infection, or medication
- Dehydration — reduced blood flow to the kidneys concentrates creatinine in the blood
- High muscle mass — bodybuilders and athletes may have naturally higher creatinine because muscles produce more of it
- High-protein diet — consuming large amounts of cooked meat (especially red meat) shortly before testing can temporarily raise levels
- Creatine supplements — supplemental creatine is converted to creatinine in the body
- Medications — certain drugs including NSAIDs, ACE inhibitors, some antibiotics, and trimethoprim can raise creatinine
- Urinary tract obstruction — kidney stones or an enlarged prostate blocking urine flow
- Congestive heart failure — reduced blood flow to the kidneys from poor heart function
Severity matters. A creatinine of 1.4 mg/dL in a muscular man may be perfectly normal, while the same reading in a small-framed woman could signal kidney impairment. This is why eGFR — which adjusts for these factors — is a more reliable indicator than creatinine alone. Persistently elevated creatinine over multiple tests is more concerning than a single elevated reading.
What Does a LOW Creatinine Level Mean?
Low creatinine levels are less common than high levels and are generally less concerning, though they can sometimes point to underlying issues.
Possible causes of low creatinine include:
- Low muscle mass — older adults, people with muscle-wasting conditions, or those who are bedridden may produce less creatinine
- Malnutrition — inadequate protein intake reduces creatinine production
- Liver disease — the liver plays a role in producing creatine, which is the precursor to creatinine
- Pregnancy — increased blood volume during pregnancy dilutes creatinine, leading to lower readings
- Overhydration — excess fluid intake can dilute creatinine in the blood
- Muscular dystrophy — progressive muscle loss reduces creatinine production over time
In many cases, slightly low creatinine in a person with a small body frame or low muscle mass is simply a reflection of body composition and not a sign of disease. A healthcare provider can help determine whether a low reading warrants further investigation.
Factors That Can Affect Your Results
Several factors can influence creatinine levels independent of kidney health. Understanding these helps avoid misinterpreting results.
- Age: Creatinine levels naturally change with age. Older adults often have lower muscle mass, which can mask declining kidney function behind a "normal" creatinine level. This is one reason eGFR is preferred over creatinine alone.
- Sex: Men generally have higher creatinine levels than women because they tend to have more muscle mass. Reference ranges are different for each sex.
- Muscle mass: Highly muscular individuals produce more creatinine and may have levels above the standard reference range without any kidney problems.
- Diet: A large serving of cooked meat (which contains creatine that converts to creatinine during cooking) within 24 hours of the test can temporarily raise levels.
- Exercise: Intense exercise, especially resistance training, can temporarily elevate creatinine due to muscle breakdown.
- Hydration: Dehydration raises creatinine; overhydration lowers it. Both can affect accuracy.
- Medications: NSAIDs (ibuprofen, naproxen), ACE inhibitors, ARBs, certain antibiotics (trimethoprim, gentamicin), and creatine supplements can all affect creatinine levels.
- Pregnancy: Blood volume increases by about 50% during pregnancy, which dilutes creatinine and results in lower-than-usual readings.
Should I Be Concerned About My Creatinine Level?
A creatinine level that is slightly outside the reference range is not automatically a reason for worry. Many factors that have nothing to do with kidney disease — such as muscle mass, diet, hydration, and recent exercise — can shift creatinine values.
One result tells only part of the story. A healthcare provider will look at the creatinine result alongside the eGFR, BUN level, the BUN-to-creatinine ratio, urine tests, and overall clinical picture. Comparing the current result to previous creatinine values (trending) is often more informative than looking at a single number.
If a result is abnormal, the next step is usually a repeat test or additional workup — not an immediate diagnosis. Kidney disease is typically diagnosed through a pattern of results over time, not from a single blood draw.
Common Next Steps
Depending on the result, a healthcare provider may recommend:
- eGFR calculation — the estimated glomerular filtration rate uses creatinine along with age, sex, and race to estimate how well the kidneys are filtering
- BUN test — blood urea nitrogen is often evaluated alongside creatinine (BUN vs. creatinine comparison)
- Urinalysis — checking urine for protein, blood, or other abnormalities that may indicate kidney damage
- Urine albumin-to-creatinine ratio (UACR) — screens for early kidney damage by measuring protein leakage into urine
- Repeat creatinine test — to confirm the result and check for trends over time
- Kidney ultrasound — imaging to evaluate kidney size, structure, and rule out obstruction
- Medication review — adjusting or stopping drugs that may be affecting kidney function
- Referral to a nephrologist — a kidney specialist for further evaluation if chronic kidney disease is suspected
Frequently Asked Questions
What is a normal creatinine level?
Normal creatinine levels are generally 0.7–1.3 mg/dL for adult men and 0.6–1.1 mg/dL for adult women. These ranges can vary slightly between laboratories. Men tend to have higher levels because they typically have more muscle mass, and creatinine is a byproduct of muscle metabolism.
What is eGFR and how does it relate to creatinine?
eGFR (estimated glomerular filtration rate) is a calculation that uses the creatinine level along with age, sex, and body size to estimate how well the kidneys are filtering blood. An eGFR above 60 is generally considered normal. An eGFR below 60 for three or more months may indicate chronic kidney disease. eGFR is considered more accurate than creatinine alone because it accounts for individual differences in body composition.
What is the difference between BUN and creatinine?
Both are waste products filtered by the kidneys, but they come from different sources. BUN (blood urea nitrogen) comes from the breakdown of protein in food and in the body. Creatinine comes from normal muscle metabolism. They are almost always tested together, and the ratio between them (BUN-to-creatinine ratio) helps distinguish kidney problems from other conditions like dehydration or gastrointestinal bleeding. Learn more in the BUN vs. creatinine comparison.
Can dehydration raise creatinine?
Yes. Dehydration is one of the most common reasons for a mildly elevated creatinine result. When the body is dehydrated, blood becomes more concentrated and blood flow to the kidneys decreases, leading to temporarily higher creatinine. Proper hydration before a blood test can help ensure more accurate results.
Does eating meat before the test affect results?
Yes. Cooked meat contains creatine, which is converted to creatinine in the body. Eating a large portion of red meat within 24 hours of the test can temporarily raise creatinine levels by up to 30%. Some healthcare providers recommend avoiding heavy meat consumption the day before a creatinine test for the most accurate results.
Can creatine supplements affect creatinine levels?
Yes. Creatine supplements, commonly used by athletes and bodybuilders, are broken down into creatinine in the body. Regular creatine supplementation can raise serum creatinine levels without any actual change in kidney function. It is important to inform a healthcare provider about supplement use so that results can be interpreted correctly.
Why are reference ranges different for men and women?
Creatinine is a byproduct of muscle metabolism, and the amount produced is directly related to muscle mass. On average, men have greater muscle mass than women, so they produce more creatinine and have higher baseline levels. This is why the normal range for men (0.7–1.3 mg/dL) is higher than for women (0.6–1.1 mg/dL).
What are the stages of chronic kidney disease?
Chronic kidney disease is classified into 5 stages based on eGFR: Stage 1 (eGFR 90+, kidney damage with normal function), Stage 2 (eGFR 60–89, mild decrease), Stage 3a (eGFR 45–59, mild to moderate), Stage 3b (eGFR 30–44, moderate to severe), Stage 4 (eGFR 15–29, severe), and Stage 5 (eGFR below 15, kidney failure). Higher creatinine levels generally correspond to lower eGFR and more advanced stages.
Is creatinine included in routine blood work?
Yes. Creatinine is included in the Comprehensive Metabolic Panel (CMP) and the Basic Metabolic Panel (BMP), both of which are among the most commonly ordered blood tests. It is routinely checked during annual physicals, hospital admissions, and before starting medications that can affect the kidneys.
Sources
- National Kidney Foundation. Estimated Glomerular Filtration Rate (eGFR). 2024.
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.
- MedlinePlus. Creatinine Test. U.S. National Library of Medicine.
- Levey AS, et al. A new equation to estimate glomerular filtration rate. Ann Intern Med. 2009;150(9):604-612.
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Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice. Reference ranges vary by laboratory, testing method, and individual factors. Always discuss your results with a qualified healthcare provider.