Waste product filtered by kidneys
21 of 22 providers
Kidney Function
Men:0.74-1.35 mg/dL, Women:0.59-1.04 mg/dL
Creatinine is a waste product produced by your muscles from the breakdown of creatine phosphate, a molecule that stores energy for muscle contraction. Your body produces creatinine at a relatively constant rate based on your muscle mass—typically 1-2 grams per day. This waste product is filtered out of your blood by your kidneys and excreted in urine.
Because creatinine production is steady and it is freely filtered by the kidneys without being reabsorbed, serum creatinine serves as an excellent marker of kidney filtration function. When kidney function declines, creatinine accumulates in the blood and serum levels rise. However, creatinine is not perfect:it is affected by muscle mass, age, sex, diet (cooked meat intake), and certain medications.
Creatinine is used to calculate eGFR (estimated glomerular filtration rate), which provides a more accurate assessment of kidney function than creatinine alone. Because muscular individuals naturally have higher creatinine, and elderly or frail individuals have lower creatinine, the absolute value must be interpreted in context. Small changes in creatinine can represent significant changes in kidney function, especially at lower baseline levels.
| Range Type | Level | Significance |
|---|---|---|
| Optimal | Men:0.8-1.2 mg/dL, Women:0.6-1.0 mg/dL | Indicates healthy kidney function with eGFR typically >90 mL/min/1.73m². Reflects good muscle mass and normal kidney filtration. Athletes and muscular individuals may be at higher end of range or slightly above without indicating kidney disease. Elderly and low muscle mass individuals may be at lower end. |
| Borderline Elevated | Men:1.2-1.5 mg/dL, Women:1.0-1.3 mg/dL | May indicate early kidney dysfunction (eGFR 60-90 mL/min) or high muscle mass. Requires investigation with eGFR calculation and urinalysis. Check for proteinuria, diabetes, hypertension. Rule out dehydration, recent high protein meal, or strenuous exercise. Retest in 3 months. If eGFR 60-90 with no other abnormalities, may be normal for muscular individuals. |
| Elevated (Stage 2-3 CKD) | Men:1.5-3.0 mg/dL, Women:1.3-2.5 mg/dL | Indicates moderate kidney dysfunction (eGFR 30-60 mL/min, Stage 2-3 CKD). Requires nephrology evaluation, investigation of underlying cause (diabetes, hypertension, glomerulonephritis), and management to slow progression. Check urinalysis for protein/blood, kidney ultrasound. Start ACE inhibitor or ARB if proteinuria present. Monitor every 3-6 months. Address cardiovascular risk factors aggressively. |
| Severely Elevated (Stage 4-5 CKD) | >3.0 mg/dL (men), >2.5 mg/dL (women) | Indicates advanced kidney disease (eGFR <30 mL/min, Stage 4-5 CKD) or acute kidney injury. Requires urgent nephrology referral. eGFR <15 mL/min (Stage 5) requires dialysis or transplant planning. Check for uremic symptoms (nausea, fatigue, confusion, pericarditis). Monitor electrolytes (potassium, phosphate), anemia, bone health. Adjust all medication dosing. Prepare for renal replacement therapy (dialysis or transplant). |
ACE inhibitors or ARBs:First-line therapy if proteinuria or diabetes present. Reduce proteinuria by 30-40% and slow CKD progression. May temporarily increase creatinine 10-20% (acceptable)
SGLT2 inhibitors:Empagliflozin, dapagliflozin slow CKD progression, especially in diabetics. Reduce cardiovascular events and kidney failure by 30-40%
Blood pressure control:Target <130/80 mmHg (or <120/80 if proteinuria >1g/day). Lower BP slows kidney damage
Glycemic control:If diabetic, target HbA1c <7% (or <6.5% if early disease without hypoglycemia risk). Poor glucose control accelerates kidney decline
Treat underlying cause:Address glomerulonephritis, autoimmune disease, obstruction, or other reversible causes
Moderate protein intake:If eGFR <60, limit to 0.6-0.8 g/kg daily to reduce kidney workload. Too low causes malnutrition;work with dietitian
Reduce sodium:<2000-2300 mg daily. High sodium worsens hypertension and proteinuria
Limit phosphate:If advanced CKD (eGFR <45), restrict phosphate-rich foods (dairy, processed foods, cola) to <800-1000 mg/day
Potassium management:If hyperkalemia (K+ >5.0), limit high-potassium foods (bananas, oranges, potatoes, tomatoes)
Adequate hydration:2-3 liters daily unless fluid restriction needed (advanced CKD with fluid retention)
Avoid nephrotoxins:NSAIDs (ibuprofen, naproxen), excessive protein supplements, herbal supplements (aristolochic acid)
Anemia treatment:If hemoglobin <10 g/dL, consider erythropoietin-stimulating agents (ESAs) and iron supplementation. Target hemoglobin 10-11.5 g/dL
Bone health:CKD causes secondary hyperparathyroidism. Monitor calcium, phosphate, PTH, vitamin D. Supplement vitamin D, use phosphate binders if needed
Metabolic acidosis:If bicarbonate <22 mEq/L, consider sodium bicarbonate supplementation to slow CKD progression
Hyperkalemia management:Avoid potassium-rich foods, use potassium binders (patiromer, sodium zirconium cyclosilicate) if needed
Cardiovascular protection:CKD greatly increases CV risk. Statin therapy, aspirin, intensive BP control reduce events
Identify cause:Pre-renal (dehydration, low blood pressure), renal (drug toxicity, contrast dye, glomerulonephritis), post-renal (obstruction from stones, enlarged prostate)
Stop nephrotoxic medications:NSAIDs, aminoglycosides, vancomycin, contrast dye, ACE inhibitors (temporarily)
Restore volume:IV fluids if dehydrated or hypotensive. Correct underlying shock or bleeding
Relieve obstruction:Foley catheter if urinary retention, urology consultation if kidney stones or prostatic obstruction
Monitor closely:Check creatinine daily until stable or improving. Watch for hyperkalemia, acidosis, volume overload
Low creatinine (<0.6 mg/dL in men, <0.5 in women) may indicate sarcopenia or malnutrition rather than superior kidney function
Resistance training:2-3x/week weight training builds muscle mass and increases creatinine to healthier levels
Adequate protein:1.2-1.6 g/kg daily, especially in elderly. Combine with exercise for muscle synthesis
Creatine supplementation:3-5g daily creatine monohydrate increases muscle creatine stores, strength, and muscle mass. Will increase creatinine slightly (normal)
Address hormones:Low testosterone in men or growth hormone deficiency can cause muscle wasting. Consider evaluation if low creatinine with low muscle mass
Serum creatinine remains normal until kidney function declines by 50% or more, making it insensitive for early CKD detection. Small changes in creatinine reflect large changes in GFR, especially at low baseline levels. A rise from 0.8 to 1.2 mg/dL represents ~40% GFR loss. eGFR equations (using creatinine, age, sex, race) improve accuracy but still miss early kidney disease. Cystatin C or direct GFR measurement may be needed in some cases.
Source:Stevens LA, et al. Assessing kidney function—measured and estimated glomerular filtration rate. N Engl J Med. 2006;354(23):2473-2483.
ACE inhibitors and ARBs reduce proteinuria and slow progression of CKD, especially in diabetic nephropathy. They may cause initial creatinine increase of 10-20% (acceptable unless rise exceeds 30%). Long-term use reduces risk of kidney failure by 20-30% and cardiovascular events by similar magnitude. Benefits outweigh initial creatinine rise in most patients.
Source:Lewis EJ, et al. Renoprotective effect of the angiotensin-receptor antagonist irbesartan in patients with nephropathy due to type 2 diabetes. N Engl J Med. 2001;345(12):851-860.
SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) slow CKD progression in diabetics and non-diabetics. The DAPA-CKD and EMPA-KIDNEY trials showed 30-40% reduction in kidney failure, cardiovascular death, or eGFR decline. Benefits persist even in advanced CKD (eGFR as low as 20-25 mL/min). Now recommended as standard therapy for CKD with proteinuria.
Source:Heerspink HJL, et al. Dapagliflozin in patients with chronic kidney disease. N Engl J Med. 2020;383(15):1436-1446.
Low-protein diets (0.6-0.8 g/kg/day) in patients with eGFR <60 mL/min reduce uremic toxin accumulation, slow GFR decline, and may delay need for dialysis by months to years. However, overly restrictive protein (<0.6 g/kg) risks malnutrition. Requires dietitian supervision and adequate calorie intake. Benefits most pronounced in Stage 4-5 CKD.
Source:Fouque D, et al. Low protein diets for chronic kidney disease in non diabetic adults. Cochrane Database Syst Rev. 2009;(3):CD001892.
Even a single episode of AKI increases risk of developing CKD by 3-10 fold and accelerates progression in those with existing CKD. Approximately 25% of patients who recover from AKI develop CKD within 1-3 years. This highlights importance of AKI prevention, prompt treatment, and long-term follow-up of creatinine and eGFR after any AKI episode.
Source:Coca SG, et al. Chronic kidney disease after acute kidney injury:a systematic review and meta-analysis. Kidney Int. 2012;81(5):442-448.
| Provider | Includes | Annual Cost | Biomarkers |
|---|---|---|---|
 Superpower | ✓ | $199 | 100+ (150 with ratios) |
 WHOOP Advanced Labs | ✓ | $349 | 65 |
 Labcorp OnDemand | ✓ | $398 | 30+ |
| ✓ | $486 | 40+ | |
| ✓ | $468 | 83 | |
| ✓ | $349 | 100+ | |
 InsideTracker | ✓ | $680 | 54 |
 Function Health | ✓ | $365 | 100+ |
| ✓ | $250 | 65 | |
| ✓ | $495 | 70+ | |
| ✓ | $895 | 100+ | |
| ✓ | $1950 | 150+ | |
| — | $399 | 100+ | |
| — | $Varies | 75+ | |
| ✓ | $190 | 100+ | |
| ✓ | $99 | 50 | |
| ✓ | $125 | 60 | |
| ✓ | $199 | 50 | |
| ✓ | $499 | 120+ | |
| ✓ | $4188 | 80+ | |
| ✓ | $375 | 85 | |
| ✓ | $700 | 129 |
21 providers include this biomarker in their panels
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
