Kreatinin (Urin-Referenzwert): the pathway in the body

Kreatinin (Urin-Referenzwert) is part of the pathway “Creatinine”. This page shows the whole pathway; the station of Kreatinin (Urin-Referenzwert) is highlighted.

Where this laboratory value sits: Creatinine — formed without an enzyme. Creatine and creatine phosphate break down slowly and without an enzyme into creatinine. The share that breaks down each day is fairly constant; the amount depends mainly on muscle mass. Source 1

In brief

Creatinine is the breakdown product of creatine and creatine phosphate, the rapid energy store of muscle. It forms without an enzyme in a fairly steady amount and leaves the body via the kidney in urine.

The pathway step by step

1. Arginine and glycine → Guanidinoacetate AGAT The enzyme AGAT transfers a guanidino group from arginine to glycine. This step occurs mainly in the kidney and the pancreas. Source 1, 2
2. Guanidinoacetate → Creatine GAMT · SAM The enzyme GAMT attaches a methyl group; it comes from SAM, the cell's methyl group donor. This forms creatine, which the liver releases into the blood. Source 1
3. Creatine → Creatine in muscle CRT (SLC6A8) · Sodium, Chloride The transporter CRT carries creatine together with sodium into the muscle cell. Meat and fish provide additional creatine from food. Most of the body's store is in skeletal muscle. Source 1
4. Creatine in muscle → Creatinine Spontaneous breakdown Creatine and creatine phosphate break down slowly and without an enzyme into creatinine. The share that breaks down each day is fairly constant; the amount depends mainly on muscle mass. Source 1
5. Creatinine → Creatinine in urine Filtration, secretion Creatinine leaves the muscle for the blood. In the kidney it passes through the glomerular filter, and a smaller share is also secreted from the blood into the urine. It therefore serves as a reference for other urine values. Source 1, 3
6. Creatine phosphate → ATP Creatine kinase · ADP When the muscle cell needs ATP quickly, the same reaction runs in reverse: creatine phosphate passes its phosphate group to ADP. Source 1

Cofactors in this pathway

• Arginine — Provides AGAT with the guanidino group for guanidinoacetate Source 1, 2In the ORY catalogue as a laboratory value: Arginin
• Glycine — Backbone to which AGAT attaches the guanidino group Source 1In the ORY catalogue as a laboratory value: Glycin
• Methionine (SAM) — As S-adenosylmethionine, provides GAMT with the methyl group for creatine Source 1In the ORY catalogue as a laboratory value: Methionin
• Sodium — Drives the transporter CRT, which carries creatine into the muscle cell Source 1In the ORY catalogue as a laboratory value: Natrium (intrazellulär)
• Chloride — Carried by the transporter CRT together with sodium and creatine Source 1
• Magnesium — Forms the complexes with ATP and ADP that creatine kinase acts on Source 1, 4In the ORY catalogue as a laboratory value: Magnesium

What acts on this pathway

• Transporter inhibitors — Some medicines block the transporters OCT2 and MATE in the kidney. The kidney then releases less creatinine into the urine, although the filter works unchanged. This relationship has been described. Source 3

Sources

1. Wyss M, Kaddurah-Daouk R. Creatine and creatinine metabolism. Physiol Rev 2000 · PubMed 10893433
2. Brosnan ME, Brosnan JT. Renal arginine metabolism. J Nutr 2004 · PubMed 15465786
3. Nakada T, Kudo T, Ito K. Quantitative Consideration of Clinical Increases in Serum Creatinine Caused by Renal Transporter Inhibition. Drug Metab Dispos 2023 · PubMed 36859345
4. de Baaij JH, Hoenderop JG, Bindels RJ. Magnesium in man: implications for health and disease. Physiol Rev 2015 · PubMed 25540137

Whole pathway: Creatinine

Related pathways

• Calcium — Natrium (intrazellulär), Magnesium
• Estradiol — Methionin, Magnesium
• GABA, glutamate and glutamine — Natrium (intrazellulär), Magnesium
• Dopamine, noradrenaline, adrenaline — Methionin, Magnesium
• Methylation: methionine and homocysteine — Glycin, Magnesium

As of 2026-09-16. Draft written by Claude to schema v2; sources checked in PubMed; expert review pending
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