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

# Vitamin C (ascorbic acid)

Vitamin C is needed to make stable collagen, absorb iron and protect against oxidative damage; its lack causes scurvy.

Updated 2026-11-01

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## Key facts

- Cofactor of prolyl and lysyl hydroxylases, which hydroxylate collagen; without it collagen cannot form a stable triple helix.
- It keeps the iron of those enzymes in the ferrous state (Fe²⁺) and reduces dietary iron so the duodenum can absorb it.
- Also used by dopamine β-hydroxylase (dopamine → noradrenaline, with copper) and carnitine synthesis.
- Deficiency: scurvy, with bleeding gums, perifollicular petechiae, corkscrew hairs and poor wound healing.

## In detail

- Sources: fresh fruit and vegetables (guava, citrus, kiwi, peppers, broccoli, potatoes). Humans cannot make it because we lost the enzyme gulonolactone oxidase. Heat and storage destroy it.
- Chemistry: ascorbate gives up two electrons and becomes dehydroascorbate; glutathione regenerates it.
- Collagen: hydroxyproline forms hydrogen bonds that stabilise the triple helix; hydroxylysine allows cross-links. Without them vessels, skin, gums and bone become fragile.
- Antioxidant: it regenerates vitamin E and neutralises radicals in the water of the cytoplasm and plasma.
- Causes of deficiency: a diet without fruit or vegetables (older adults living alone, alcoholism, eating disorders, very restrictive diets in children), smoking (raises turnover), dialysis.
- Excess (supplements): diarrhoea, oxalate kidney stones (ascorbate breaks down to oxalate) and iron overload in people with haemochromatosis.
- Lab: plasma or leucocyte ascorbate (leucocyte levels reflect stores better); scurvy is usually diagnosed clinically and by the response to treatment.

**Also called**
Ascorbic acid, Ascorbate

**Formula**
C₆H₈O₆

**PubChem**
[CID 54670067](https://pubchem.ncbi.nlm.nih.gov/compound/54670067)

## Structure

- A six-carbon lactone with an enediol group (two hydroxyls on a double bond) that gives up electrons easily.
- The L form is active; dehydroascorbate is its oxidised form.

## Clinical notes

- Taking vitamin C with meals increases absorption of non-heme iron from plant foods.
- Scurvy is still seen in children with autism or very selective diets and in adults with alcoholism or malnutrition.
- Methaemoglobinaemia can be treated with ascorbic acid when methylene blue is unavailable or contraindicated.

## Pathways

- [Catecholamine synthesis and breakdown](https://durgical.com/en/biochemistry/pathways/catecholamine-synthesis-and-breakdown/)

## Related conditions

- [Scurvy (vitamin C deficiency)](https://durgical.com/en/conditions/scurvy/)
- [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/)
- [Kidney stones (urolithiasis)](https://durgical.com/en/conditions/kidney-stones/)

## Related

- [Iron](https://durgical.com/en/biochemistry/topics/iron/)
- [Vitamin E (α-tocopherol)](https://durgical.com/en/biochemistry/molecules/vitamin-e/)
- [Copper](https://durgical.com/en/biochemistry/topics/copper/)

## Test yourself

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

## Why does lack of vitamin C make vessels and gums fragile?

Without it prolyl and lysyl hydroxylases fail; unhydroxylated collagen cannot form a stable triple helix.

## How does vitamin C help absorb iron?

It reduces dietary ferric iron (Fe³⁺) to ferrous iron (Fe²⁺), the form carried by DMT1 in the duodenum.

## Which skin signs are typical of scurvy?

Petechiae around hair follicles, corkscrew hairs, easy bruising and wounds that do not heal.

## What risks come with high-dose vitamin C supplements?

Oxalate kidney stones, diarrhoea and, in haemochromatosis, greater iron absorption.

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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: [L-Ascorbic Acid (CID 54670067)](https://pubchem.ncbi.nlm.nih.gov/compound/54670067) (PubChem, NCBI, 2026) · Public domain; [Vitamin C: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/002404.htm) (MedlinePlus, US National Library of Medicine, 2026); [Scurvy: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000355.htm) (MedlinePlus, US National Library of Medicine, 2026); [Vitamin C: MedlinePlus](https://medlineplus.gov/vitaminc.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).

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