Vitamin C optimal range and reference range

Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026

Sera's bands for Vitamin C:

Optimal 0.88 – 2 mg/dL (50 – 114 μmol/L); sufficient 0.4 – 2 mg/dL (23 – 114 μmol/L); out of range below 0.4 mg/dL.

Evidence grade: Published reference interval. A band that primarily reflects a published adult laboratory or population reference interval. It is not necessarily applicable to every assay or laboratory.

All units

Unit	Optimal	Sufficient	Out of range
mg/dL	0.88 – 2	0.4 – 2	below 0.4
μmol/L	50 – 114	23 – 114	below 23

Bounded on the low side only — a high result is not treated as out of range. A high result reflects recent intake or supplements, and no upper limit has a clinical meaning.

What the evidence says

The acceptable band starts at 23 μmol/L (0.4 mg/dL), where four laboratories agree (ARUP, Mayo, and two NHS trusts at 26), and deficiency is below about 11 μmol/L. The optimal band starts at 50 μmol/L (0.88 mg/dL), the plasma level the Nordic Nutrition Recommendations 2023, following EFSA, use to define adequate status. That is a public-health adequacy target, not an outcome threshold. High results reflect recent intake and are not flagged. The sample breaks down unless frozen and protected from light, smokers run lower, and an NHS laboratory states that the result is of no value when CRP is raised.

Sources

Vitamin C, Plasma (0080380) — ARUP Laboratories, 2026 · Laboratory / reference-interval sourceInterval 23 to 114 μmol/L; below 11 μmol/L is deficiency and 11 to 23 a moderate risk of it. Sera's sufficient band in μmol/L.
Ascorbic Acid (Vitamin C), Plasma (VITC) — Mayo Clinic Laboratories (performing laboratory), Duke University Hospital test catalog, 2026 · Laboratory / reference-interval source0.4 to 2.0 mg/dL indicates adequate supply. Sera's sufficient band in mg/dL.
Vitamin C (test information) — The Rotherham NHS Foundation Trust, Clinical Biochemistry, 2024 · Laboratory / reference-interval sourceUK plasma interval 26 to 85 μmol/L, deficiency below 11.1. Confirms the low edge within 3 μmol/L.
Vitamin C (test information) — Bradford and Craven Pathology, Bradford Teaching Hospitals NHS Foundation Trust, 2026 · Laboratory / reference-interval sourceRepeats the 26 to 85 μmol/L interval and states that the result is of no value when CRP is raised.
Nordic Nutrition Recommendations 2023: Vitamin C — Nordic Council of Ministers, 2023 · Government / public-health guidanceUses a target plasma ascorbate of 50 μmol/L, following EFSA, to set the average requirement. The start of Sera's optimal band; an adequacy target, not an outcome threshold.

What Vitamin C (Ascorbic Acid) measures

Vitamin C measured in plasma.

Reflects recent intake more than body stores. Smokers run lower, and inflammation lowers it, so a low result with a raised CRP may not mean deficiency. The sample breaks down quickly unless it is frozen and protected from light, so an unexpectedly low result is worth repeating before acting on it.

Related vitamins & minerals markers

See Vitamin C in the full list of biomarker ranges

This page is a reference for practitioners, not medical advice. Sera's bands are practitioner targets for structured review, not diagnostic thresholds, and Sera does not diagnose or recommend treatment. Read a result alongside the interval printed by the issuing laboratory and the client's history and symptoms. Range set: Sera Production, version 1.0, last reviewed November 9, 2026.