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Vitamins & Minerals

Magnesium (Serum)

In the UK, the standard clinical (NHS) reference range for Magnesium (Serum) is 0.7-1.0 mmol/L, with 0.85-1.0 mmol/L considered the performance-optimised range. A result within these ranges suggests typical status; only a qualified clinician can interpret an individual reading.

Magnesium is an essential mineral involved in over 300 enzymatic reactions in the body, including energy production, protein synthesis, muscle and nerve function, and blood pressure regulation. Serum magnesium reflects only about 1% of total body stores, as most magnesium resides in bones and soft tissues — making subclinical deficiency difficult to detect.

Last reviewed: 11 June 2026

Optimal Ranges

What is the optimal range for Magnesium?

Clinical (NHS) Range

0.7-1.0 mmol/L

mmol/L

Performance-Optimised Range

0.85-1.0 mmol/L

mmol/L

Magnesium (Serum) reference ranges (UK)
RangeValueUnit
Clinical (NHS) reference range0.7-1.0 mmol/Lmmol/L
Performance-optimised range0.85-1.0 mmol/Lmmol/L

The clinical range defines what is considered medically “normal” — broad enough to cover 95% of the population. The performance range reflects where research and clinical experience suggest most people feel and function at their best. A result in either range suggests typical status and is not a diagnosis; any individual reading should be interpreted by a qualified clinician.

Why It Matters

Why Magnesium matters for performance

Magnesium is arguably the most underappreciated performance mineral. It directly influences sleep quality, testosterone production, insulin sensitivity, and muscle recovery. Studies show that magnesium supplementation in men with low intake increases both free and total testosterone. Most Western diets are deficient in magnesium due to soil depletion and processed food consumption. For men who sweat heavily during training, losses are amplified further.

Symptoms

What are the symptoms of low or high Magnesium?

Low / Deficiency

  • Muscle cramps and spasms
  • Poor sleep quality and insomnia
  • Anxiety and restlessness
  • Heart palpitations
  • Fatigue despite adequate rest
  • Headaches and migraines

High / Excess

  • Diarrhoea and nausea
  • Low blood pressure
  • Muscle weakness
  • Irregular heartbeat (rare, usually from supplementation)

Dietary Sources

Which foods support Magnesium levels?

Dark chocolate (85%+)Pumpkin seeds and almondsSpinach and Swiss chardAvocadoBlack beans and lentilsWhole grains (quinoa, brown rice)

Supplementation

How do you improve Magnesium levels?

Magnesium glycinate (or bisglycinate) is the preferred form for sleep and recovery — well-absorbed and least likely to cause GI issues. Magnesium L-threonate has emerging evidence for cognitive benefits. Typical dose: 300-400 mg elemental magnesium daily, ideally taken in the evening. Avoid magnesium oxide — cheap but poorly absorbed. Pair with vitamin B6 for enhanced cellular uptake.

Testing

How is Magnesium tested in the UK?

Magnesium is measured from a blood sample. With Helvy, that means a finger-prick kit taken at home and posted to a UKAS-accredited UK laboratory, with results in around 5 days, reviewed by a qualified clinician. Your result is reported against both the clinical range (0.7-1.0 mmol/L) and the performance-optimal range (0.85-1.0 mmol/L), so you can see not just whether you are “normal” but whether you are optimal. If you make a change, retest after 8-12 weeks to confirm it worked.

Research

Key study

Magnesium and anabolic hormones in older men

Cinar V, Polat Y, Baltaci AK, Mogulkoc R

International Journal of Endocrinology (2011)

DOI: 10.1155/2011/649285

Related Biomarkers

Vitamins & Minerals

Vitamin D (25-OH)

Optimal: 100-150 nmol/L

Hormones

Total Testosterone

Optimal: 20-30 nmol/L

Metabolic

HbA1c (Glycated Haemoglobin)

Optimal: 20-34 mmol/mol (below 5.4%)

Related Guides

Explore Magnesium in depth

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Serum, RBC & ionised magnesium

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Athlete Blood Test UK

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Test your Magnesium levels

Magnesium is included in the Helvy 50+ biomarker panel. Get your results in 5 days with a personalised protocol.

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This content is for educational purposes only and does not constitute medical advice. Your data suggests areas for optimisation, but any concerns should be discussed with a qualified healthcare professional. If your results flag values outside safe ranges, we recommend consulting your GP.