Serum magnesium 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 Serum magnesium:
- Optimal 2.07 – 2.3 mg/dL (0.85 – 0.95 mmol/L); sufficient 1.7 – 2.4 mg/dL (0.7 – 1 mmol/L); out of range below 1.7 or above 2.4 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 | 2.07 – 2.3 | 1.7 – 2.4 | below 1.7 or above 2.4 |
| mmol/L | 0.85 – 0.95 | 0.7 – 1 | below 0.7 or above 1 |
| mEq/L | 1.7 – 1.9 | 1.4 – 2 | below 1.4 or above 2 |
What the evidence says
The acceptable band follows laboratory reference intervals: 1.7 mg/dL (0.70 mmol/L) is the lower limit used by MedlinePlus, Mayo Clinic Laboratories and UK laboratories, and 1.0 mmol/L (2.4 mg/dL) is the UK upper limit; US laboratories stop at 2.2 to 2.3 mg/dL. The optimal band starts at 0.85 mmol/L (2.07 mg/dL), the lower limit a group of magnesium researchers recommended in 2022 on the grounds that lower values can hide a chronic deficit; few laboratories have adopted it. Serum magnesium is a rough guide to body stores and can be normal when stores are low.
Sources
- Magnesium blood test — MedlinePlus Medical Encyclopedia, US National Library of Medicine, 2025 · Government / public-health guidanceNormal blood magnesium is 1.7 to 2.2 mg/dL (0.70 to 0.91 mmol/L). Matches Sera's sufficient lower edge of 1.7 mg/dL exactly; its upper limit of 2.2 is well under Sera's 2.6.
- MGS - Magnesium, Serum — Mayo Clinic Laboratories Test Catalog, 2026 · Laboratory / reference-interval sourceReference values over 17 years are 1.7 to 2.3 mg/dL. Matches Sera's sufficient lower edge of 1.7; the 2.3 upper limit equals Sera's optimal upper edge and is below its sufficient upper edge of 2.6. Current catalogue entry, opened October 2026.
- Magnesium — Worcestershire Acute Hospitals NHS Trust, Pathology tests A to Z, 2026 · Laboratory / reference-interval sourceReference range from 30 days of age is 0.7 to 1.0 mmol/L, attributed to the UK Pathology Harmony ranges. Supports the 0.70 mmol/L lower edge and an upper edge of 1.00 mmol/L (2.4 mg/dL) in place of Sera's 1.05 (2.6 mg/dL). The page is undated.
- Recommendation on an updated standardization of serum magnesium reference ranges — Rosanoff A, West C, Elin RJ, et al. — European Journal of Nutrition, 2022 · Peer-reviewed publicationRecommends 0.85 mmol/L (2.07 mg/dL; 1.7 mEq/L) as the lower reference limit for serum magnesium, to avoid counting people with chronic latent magnesium deficit as normal. Only 2 of 43 laboratory ranges surveyed used it. Sera's optimal lower edge of 2.0 mg/dL (0.82 mmol/L) is close but lower.
What Magnesium (Serum) measures
The amount of magnesium in your blood serum. Any excess is removed by the kidneys.
Less accurate than RBC magnesium but commonly tested. Low levels can mean deficiency, while high levels can happen when kidney function is reduced.