Magnesium is one of the busiest minerals in the body, involved in hundreds of chemical reactions. It helps your muscles contract and relax, keeps nerves firing correctly, supports a steady heartbeat and plays a part in bone health and energy production. Despite this, it rarely gets much attention until something feels off.
What magnesium does
Most of the body's magnesium is stored in bone and inside cells, with only a small amount circulating in the blood. It acts as a cofactor for enzymes that turn food into energy, regulate the nervous system and keep the electrical activity of the heart in rhythm. It also works in balance with other minerals such as calcium and potassium, which is one reason a shortfall can have knock-on effects.
Signs you might be running low
Mild magnesium deficiency can be subtle and easy to overlook. When symptoms do appear, they often reflect the mineral's role in muscle and nerve function:
- Muscle cramps, twitches or spasms
- Fatigue and general weakness
- Tingling or numbness
- Heart palpitations or an irregular heartbeat
- Low mood, irritability or poor sleep
These symptoms are non-specific, meaning they can have many causes. That is exactly why guessing is unreliable and a blood test is helpful when magnesium is a genuine suspect.
Common causes of deficiency
A number of factors can deplete magnesium over time. A diet low in whole grains, nuts, seeds and leafy greens is a common contributor. Other causes include digestive conditions that reduce absorption, persistent diarrhoea or vomiting, certain medications such as some diuretics and long-term stomach-acid reducers, poorly controlled diabetes, and regular high alcohol intake. Older adults are also more prone to low levels.
How magnesium is tested
A blood test measures the magnesium circulating in your serum. It is worth knowing that because most magnesium is stored inside cells and bone, blood levels can stay within range even when body stores are modestly depleted. Even so, a blood test remains a practical and widely used way to check, particularly when symptoms or risk factors point towards a shortfall. Your clinician will interpret the result alongside your symptoms and any related minerals.
When to consider a test
Testing can be worthwhile if you have unexplained cramps, palpitations or persistent fatigue, if you take medications known to lower magnesium, or if you have a condition that affects absorption. As with any single result, magnesium is best understood in context rather than in isolation, and any deficiency should be investigated for its cause.
Check your magnesium
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Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic