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

# β-Hydroxybutyrate

β-Hydroxybutyrate is the most abundant ketone body in blood; it is measured to diagnose and follow ketoacidosis.

Updated 2026-11-01

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## Key facts

- Formed by reducing acetoacetate with NADH (BDH1); the physiological isomer is D (R).
- In fasting it is about 3 times more abundant than acetoacetate; in ketoacidosis, up to 10 times.
- Strictly it is not a ketone (it has a hydroxyl group), but it is grouped with the ketone bodies.
- Capillary blood measurement is the preferred way to monitor diabetic ketoacidosis.

**Also called**
D-3-hydroxybutyrate, (R)-3-Hydroxybutanoic acid

**Formula**
C₄H₈O₃

**PubChem**
[CID 92135](https://pubchem.ncbi.nlm.nih.gov/compound/92135)

## Structure

- A 4-carbon acid with a hydroxyl at C3; negatively charged at physiological pH.

## Clinical notes

- High β-hydroxybutyrate with a raised anion gap points to diabetic, alcoholic or starvation ketoacidosis.
- Besides fuel, it acts as a signal (inhibits histone deacetylases) and restrains lipolysis.

## Pathways

- [Ketogenesis (ketone body synthesis)](https://durgical.com/en/biochemistry/pathways/ketogenesis/)

## Related conditions

- [Diabetic ketoacidosis](https://durgical.com/en/conditions/diabetic-ketoacidosis/)
- [Type 1 diabetes mellitus](https://durgical.com/en/conditions/type-1-diabetes-mellitus/)

## Related

- [Acetoacetate (acetoacetic acid)](https://durgical.com/en/biochemistry/molecules/acetoacetate/)
- [β-Hydroxybutyrate dehydrogenase (BDH1)](https://durgical.com/en/biochemistry/enzymes/hydroxybutyrate-dehydrogenase/)
- [Succinyl-CoA:3-ketoacid CoA transferase (SCOT)](https://durgical.com/en/biochemistry/enzymes/succinyl-coa-3-ketoacid-coa-transferase/)
- [Mitochondrial HMG-CoA synthase (HMGCS2)](https://durgical.com/en/biochemistry/enzymes/mitochondrial-hmg-coa-synthase/)
- [NAD⁺ (nicotinamide adenine dinucleotide)](https://durgical.com/en/biochemistry/molecules/nad/)

## Test yourself

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

## What is the most abundant ketone body in diabetic ketoacidosis?

β-Hydroxybutyrate, because high NADH pushes the BDH1 reaction.

## Why is blood β-hydroxybutyrate preferred to urine ketones?

The urine strip detects acetoacetate and can underestimate ketosis or track recovery poorly.

## Is β-hydroxybutyrate chemically a ketone?

No: it is a hydroxy acid, although it is classed with the ketone bodies.

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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: [3-Hydroxybutanoic acid, (R)- (CID 92135)](https://pubchem.ncbi.nlm.nih.gov/compound/92135) (PubChem, NCBI, 2026) · Public domain; [Synthesis of Ketone Bodies](https://reactome.org/PathwayBrowser/#/R-HSA-77111) (Reactome, 2026); [Ketones blood test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003498.htm) (MedlinePlus, US National Library of Medicine, 2026).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/molecules/hydroxybutyrate/