[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Creatinine and estimated glomerular filtration rate (eGFR)

[Biochemistry](https://durgical.com/en/biochemistry/) · Topic

# Creatinine and estimated glomerular filtration rate (eGFR)

Creatinine comes from muscle and is filtered by the kidney; it is used to estimate how much the glomeruli filter.

Updated 2026-11-01

## Key facts

- Creatinine forms non-enzymatically and at a steady rate from muscle creatine and phosphocreatine.
- It is freely filtered and slightly secreted by the tubule; its level rises when glomerular filtration falls.
- The relation is not linear: early on, nearly half of filtration can be lost with little change in creatinine.
- eGFR is calculated with equations (race-free CKD-EPI 2021) from creatinine, age and sex; cystatin C improves the estimate.
- Chronic kidney disease (KDIGO): low GFR (
- What it measures: serum creatinine concentration (Jaffe or enzymatic method). eGFR is not measured: it is calculated.
- Where it comes from: about 1–2 % of muscle creatine becomes creatinine each day; so it depends on muscle mass and on meat eaten.
- Why it rises: acute kidney injury (prerenal, renal, postrenal), chronic kidney disease, rhabdomyolysis, recent cooked meat, creatine supplements.
- Pitfalls: people with little muscle (older adults, amputees, people with cirrhosis or malnutrition) have a 'normal' creatinine with low filtration; trimethoprim and cimetidine block tubular secretion and raise creatinine without lowering filtration; ketones and some cephalosporins interfere with the Jaffe method.
- eGFR equations do not apply when function is changing fast (acute kidney injury): then the change in creatinine and urine output is followed.
- 24-hour urine creatinine clearance overestimates filtration because of tubular secretion and depends on a complete collection.

**Also called**
Serum creatinine, GFR, eGFR, CKD-EPI, Creatinine clearance

## Clinical notes

- Acute kidney injury (KDIGO) is defined by a rise in creatinine within 48 h or 7 days, or by low urine output for hours.
- eGFR guides dose adjustment of renally cleared drugs (metformin, aminoglycosides, direct anticoagulants).
- Diabetes and hypertension are the leading causes of chronic kidney disease in Colombia and worldwide.

## Related conditions

- [Acute kidney injury](https://durgical.com/en/conditions/acute-kidney-injury/)
- [Chronic kidney disease](https://durgical.com/en/conditions/chronic-kidney-disease/)
- [Type 2 diabetes mellitus](https://durgical.com/en/conditions/type-2-diabetes-mellitus/)
- [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/)
- [Autosomal dominant polycystic kidney disease](https://durgical.com/en/conditions/autosomal-dominant-polycystic-kidney-disease/)

## Related

- [Urea and blood urea nitrogen (BUN) as lab tests](https://durgical.com/en/biochemistry/topics/urea-and-blood-urea-nitrogen-as-lab-tests/)
- [Creatine kinase (CK) and CK-MB as lab tests](https://durgical.com/en/biochemistry/topics/creatine-kinase-and-ck-mb-as-lab-tests/)
- [Molecules derived from amino acids](https://durgical.com/en/biochemistry/topics/molecules-derived-from-amino-acids/)
- [Urinalysis](https://durgical.com/en/biochemistry/topics/urinalysis/)

## Test yourself

Think of the answer, then tap the question to see it.

## Where does serum creatinine come from?

From the spontaneous, steady conversion of muscle creatine and phosphocreatine; so it depends on muscle mass.

## Why does a normal creatinine not rule out low kidney function in a frail older adult?

Low muscle mass makes little creatinine, so filtration can be reduced with an apparently normal value.

## What defines chronic kidney disease by KDIGO?

A GFR below 60 mL/min/1.73 m² or a marker of kidney damage (such as albuminuria) lasting more than 3 months.

## Why can trimethoprim raise creatinine without harming the kidney?

It blocks tubular secretion of creatinine, so the level rises although glomerular filtration does not change.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/biochemistry/topics/creatinine-and-estimated-glomerular-filtration-rate/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Creatinine Test: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/creatinine-test/) (MedlinePlus, US National Library of Medicine, 2026); [Estimated Glomerular Filtration Rate (eGFR) and GFR Tests: MedlinePlus Medical Test](https://medlineplus.gov/lab-tests/estimated-glomerular-filtration-rate-egfr-and-gfr-tests/) (MedlinePlus, US National Library of Medicine, 2026); [Creatinine blood test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003475.htm) (MedlinePlus, US National Library of Medicine, 2026); [Kidney Tests: MedlinePlus](https://medlineplus.gov/kidneytests.html) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

[← All of biochemistry](https://durgical.com/en/biochemistry/)

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/biochemistry/topics/creatinine-and-estimated-glomerular-filtration-rate/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/topics/creatinine-and-estimated-glomerular-filtration-rate/