Magnesium
| Clinical | Optimal | |
|---|---|---|
| Male | 0.70 - 1.00 mmol/L | 0.75–1.00 mmol/L |
| Female | 0.70 - 1.00 mmol/L | 0.75–1.00 mmol/L |
What is Magnesium?
Magnesium is the fourth most abundant mineral in your body and is involved in over 300 different enzymatic reactions. Your blood test measures serum magnesium — the amount circulating in your bloodstream. However, only about 1% of your total body magnesium is found in the blood, with the rest stored in bones, muscles, and soft tissues.
This means serum magnesium can appear normal even when your overall body stores are depleted — it is a late marker of deficiency. By the time serum magnesium drops below the reference range, total body magnesium may already be significantly low.
Magnesium acts as a cofactor for enzymes involved in energy production (ATP), protein synthesis, muscle and nerve function, blood sugar regulation, and blood pressure control. It truly is a workhorse mineral.
Why Magnesium Matters for Your Health
Magnesium deficiency is increasingly recognised as a widespread issue in modern diets, with some estimates suggesting up to 60% of adults in Western countries do not meet their daily requirement. Soil depletion, food processing, and increased consumption of refined foods have all contributed to lower magnesium intake.
For longevity, magnesium is critical. It supports cardiovascular health by helping regulate heart rhythm and blood pressure. It plays a key role in insulin sensitivity and blood sugar control. It is essential for bone density (your bones contain about 60% of your magnesium). And it profoundly influences sleep quality and stress resilience.
Research has linked higher magnesium intake with reduced risk of type 2 diabetes, cardiovascular events, and all-cause mortality. It is one of the most underappreciated minerals for long-term health.
Magnesium& Your Wearable Data
Magnesium is involved in over 300 enzymatic reactions including muscle contraction, nerve function, energy production, and sleep regulation. Serum magnesium only reflects about 1% of total body stores, so even normal blood levels may coexist with tissue deficiency. Wearable data helps identify magnesium-related patterns: deficiency is associated with muscle cramps, poor sleep quality, elevated resting heart rate, and reduced HRV.
Exercise increases magnesium requirements and losses through sweat. Wearable data showing high training volumes, particularly in warm conditions, indicates greater magnesium depletion risk. Magnesium deficiency impairs exercise performance, and your wearable may show this as reduced power output, earlier fatigue onset, and slower recovery between sessions.
Magnesium's role in sleep is well-established and measurable through wearables. Deficiency is associated with difficulty falling asleep, reduced deep sleep, and nighttime awakenings. If your wearable sleep data shows poor sleep quality that improves with magnesium supplementation, this provides practical evidence of its benefit for your individual physiology.
What High Magnesium May Suggest
High serum magnesium (hypermagnesaemia) is uncommon and almost always related to excessive supplementation, kidney disease (reduced excretion), or certain medications like magnesium-containing antacids or laxatives used in large quantities.
Mild elevations may cause no symptoms. Moderate to severe hypermagnesaemia can cause nausea, flushing, muscle weakness, low blood pressure, and drowsiness. Very severe cases (which are rare) can affect heart rhythm and breathing.
If your magnesium is elevated and you are not supplementing heavily, your GP may wish to check your kidney function. For most people, simply adjusting supplement doses resolves the issue.
What Low Magnesium May Suggest
Low serum magnesium suggests your circulating levels are depleted, and since blood represents only 1% of total body magnesium, your overall stores may be more significantly depleted than the number suggests.
Common causes include inadequate dietary intake (very common), chronic stress (which increases magnesium excretion), excessive alcohol consumption, gastrointestinal conditions affecting absorption, certain diuretic medications, type 2 diabetes, and heavy sweating from intense exercise.
Symptoms of magnesium deficiency can be subtle and wide-ranging: muscle cramps and twitches, difficulty sleeping, anxiety, irritability, headaches, fatigue, heart palpitations, and constipation. Many people attribute these symptoms to stress or ageing when the underlying cause may be correctable with improved magnesium intake.
How to Optimise Your Magnesium
Food
Focus on magnesium-rich foods: dark leafy greens (spinach, Swiss chard, kale), pumpkin seeds, almonds, cashews, dark chocolate (85%+), avocado, black beans, and whole grains. Bananas, salmon, and figs are also good sources. Mineral-rich water can contribute meaningfully to daily intake. Aim for variety rather than relying on a single source.
Lifestyle
Reduce chronic stress, which depletes magnesium rapidly. Limit alcohol consumption, as it increases urinary magnesium loss. Moderate caffeine intake for the same reason. Regular exercise supports magnesium utilisation but ensure you replenish after heavy sweating. Epsom salt (magnesium sulphate) baths may provide some transdermal absorption and promote relaxation, though oral intake is the primary route.
Supplements
Magnesium glycinate is well absorbed and gentle on the stomach, making it ideal for general supplementation and sleep support. Magnesium threonate may specifically benefit brain health and cognitive function. A typical dose is 200–400 mg elemental magnesium daily, taken in the evening. Avoid magnesium oxide, which has poor absorption and mainly acts as a laxative.
⚠️ Supplement Warning
Caution with magnesium supplementation. While magnesium supplementation is generally safe for most adults, excessive doses can cause diarrhoea, nausea, and abdominal cramping. In individuals with kidney impairment, magnesium can accumulate to dangerous levels causing cardiac arrhythmias and respiratory depression. The tolerable upper limit for supplemental magnesium is 350 mg/day for adults. Magnesium supplements can interact with antibiotics, diuretics, and heart medications. Consult a healthcare professional before supplementing, particularly if you have kidney disease or take prescription medications.
When to Speak to Your GP
See your GP if serum magnesium is below 0.70 mmol/L or if you experience persistent muscle cramps, heart palpitations, or numbness and tingling that does not improve with dietary changes and supplementation. Also consult your GP if you have kidney disease or take medications that affect magnesium levels, as dosing may need professional guidance.
References
- NHS. Vitamins and minerals — Others. Updated 2024. nhs.uk
- BMJ. Fiorentini D, et al. Magnesium: biochemistry, nutrition, detection, and social impact of diseases linked to its deficiency. Nutrients. 2021;13(4):1136. pubmed.ncbi.nlm.nih.gov
- NEJM. de Baaij JHF, et al. Magnesium in man: implications for health and disease. Physiol Rev. 2015;95(1):1-46. pubmed.ncbi.nlm.nih.gov
- NICE. Hypomagnesaemia — Clinical Knowledge Summaries. cks.nice.org.uk
Medical Disclaimer— This content is for general educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Omniwo Ltd is a wellness information service and is not a medical device, clinical laboratory, or regulated healthcare provider under MHRA guidelines. The “optimal ranges” presented on this page are based on published clinical guidelines (WHO, NICE, NHS) and peer-reviewed research; they represent functional wellness targets and may differ from standard laboratory reference ranges. Individual results should always be interpreted by a qualified healthcare professional (such as your GP) who understands your full medical history. Do not start, stop, or change any medication or supplement based solely on this information. If you are experiencing symptoms, seek medical attention promptly.