[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Uric acid

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

# Uric acid

Uric acid is the final product of purines in humans; when it builds up, it forms crystals that cause gout and stones.

Updated 2026-11-01

Loading the 3D model…

## Key facts

- Xanthine oxidase makes it from xanthine; humans have no uricase to break it down.
- At blood pH it is mostly monosodium urate, which saturates above about 6.8 mg/dL.
- Two-thirds are excreted by the kidney (filtered and reabsorbed mainly by URAT1) and one-third by the gut.
- In acidic urine it precipitates as uric acid: radiolucent stones.

**Also called**
Urate

**Formula**
C₅H₄N₄O₃

**PubChem**
[CID 1175](https://pubchem.ncbi.nlm.nih.gov/compound/1175)

## Structure

- A purine with three oxo groups (2,6,8-trioxypurine); its first pKa is about 5.4.
- It is a major plasma antioxidant.

## Clinical notes

- Hyperuricaemia from overproduction (tumour lysis, HGPRT deficiency) or, more often, from low renal excretion (kidney disease, diuretics, alcohol).
- It is lowered with xanthine oxidase inhibitors, uricosurics or recombinant uricase, depending on the case.
- A very low uric acid points to xanthinuria, PNP deficiency or Fanconi syndrome.

## Drugs that act here

- [Rasburicase](https://durgical.com/en/pharmacology/rasburicase/)
- [Pegloticase](https://durgical.com/en/pharmacology/pegloticase/)

## Pathways

- [Purine degradation and salvage](https://durgical.com/en/biochemistry/pathways/purine-degradation-and-salvage/)

## Related conditions

- [Gout](https://durgical.com/en/conditions/gout/)
- [Kidney stones (urolithiasis)](https://durgical.com/en/conditions/kidney-stones/)
- [Tumour lysis syndrome](https://durgical.com/en/conditions/tumour-lysis-syndrome/)
- [Lesch-Nyhan syndrome](https://durgical.com/en/conditions/lesch-nyhan-syndrome/)
- [Hereditary xanthinuria](https://durgical.com/en/conditions/hereditary-xanthinuria/)

## Related

- [Xanthine oxidase](https://durgical.com/en/biochemistry/enzymes/xanthine-oxidase/)
- [Hypoxanthine](https://durgical.com/en/biochemistry/molecules/hypoxanthine/)
- [Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)](https://durgical.com/en/biochemistry/enzymes/hypoxanthine-guanine-phosphoribosyltransferase/)
- [Drugs acting on nucleotide metabolism](https://durgical.com/en/biochemistry/topics/drugs-acting-on-nucleotide-metabolism/)

## Test yourself

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

## Why do uric acid stones form in acidic urine?

At low pH the undissociated form predominates, which is far less soluble than urate.

## What is the most common cause of hyperuricaemia?

Low renal urate excretion, rather than overproduction.

## What does an almost undetectable uric acid suggest?

A xanthine oxidase defect (xanthinuria), PNP deficiency or renal loss (Fanconi syndrome).

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/biochemistry/molecules/uric-acid/)

Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.

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

Sources: [Uric Acid (CID 1175)](https://pubchem.ncbi.nlm.nih.gov/compound/1175) (PubChem, NCBI, 2026) · Public domain; [Uric acid - blood: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003476.htm) (MedlinePlus, US National Library of Medicine, 2026); [Purine catabolism](https://reactome.org/PathwayBrowser/#/R-HSA-74259) (Reactome, 2026).

[← 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/molecules/uric-acid/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/molecules/uric-acid/