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Muscle cramps, poor sleep, palpitations, fatigue. A magnesium check is one of the simplest and most actionable nutritional tests available.
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Check your serum magnesium level to investigate muscle cramps, fatigue, palpitations, or poor sleep. Simple home fingerstick kit. GMC physician review.
Magnesium is a cofactor in over 300 enzymatic reactions, including ATP synthesis, DNA replication, muscle contraction, and nerve signal transmission. Despite this fundamental role, dietary surveys consistently show that a significant proportion of UK adults consume below the recommended daily intake, and those with high stress levels, regular alcohol consumption, or type 2 diabetes are at particular risk of deficiency. The problem with serum magnesium is that the body prioritises maintaining blood levels even at the expense of intracellular stores, meaning deficiency must be fairly pronounced before serum values fall outside the reference range. For this reason, a low serum magnesium is a clinically meaningful finding that warrants attention. Symptoms such as muscle twitching, cramps, fatigue, palpitations, and insomnia are commonly associated with marginal magnesium status and may not resolve until stores are addressed. Results are reviewed by a GMC-registered physician.
Understand what each marker measures, why it matters, and what the science says — not just a list of numbers.
This panel is designed for adults who want a comprehensive, evidence-based picture of their metabolic health — not a GP referral panel.
People with recurrent muscle cramps or restless legs at night
Individuals experiencing palpitations or irregular heartbeat not yet investigated
Anyone with chronic stress, poor sleep, or anxiety wanting to rule out a nutritional component
Athletes who sweat heavily or train in hot environments
People with type 2 diabetes or taking diuretics, which both increase urinary magnesium loss
Serum magnesium is maintained within a narrow range by the kidneys, which excrete or retain magnesium to keep blood levels stable. This means that serum magnesium is an insensitive marker of total body magnesium; intracellular deficiency can exist with a normal serum result. A low serum magnesium is therefore a late and significant finding, but a normal result does not guarantee adequate intracellular stores. For a more sensitive assessment of magnesium status, red cell magnesium or a magnesium loading test can be requested through your GP. This panel does not include associated electrolytes such as calcium, potassium, or phosphate, which should be considered alongside magnesium in cardiac or neuromuscular symptoms.
From order to physician-reviewed report in as little as three working days.
Home fingerstick or mobile phlebotomist at checkout.
No fasting required; instructions included.
Pre-paid Royal Mail envelope included.
Secure online report with physician commentary in 3 to 5 working days.
Three options designed to fit your schedule, location, and preference — all producing a laboratory-standard sample.
Adults 18+ in mainland UK. Not suitable if you have had a transfusion in the last 3 months.
Order anytime; kit dispatched within 24 hours Mon–Fri.
Allow 24–48 hours for sample transit on top of lab processing time.
Adults 18+ within 20 miles of a serviced city centre.
Mon–Sun, 06:00–20:00. Next-day booking typical.
Sample reaches the lab within 24 hours of collection.
Adults 16+ with photo ID. Paediatric draws by appointment at selected sites.
Mon–Fri, with Saturday hours at most metropolitan locations.
Samples processed same-day at the receiving clinic.
Every test is processed in a UKAS ISO 15189-accredited laboratory, overseen by GMC-registered physicians, and governed by UK GDPR. No overseas processing, no offshore data.
Follow these guidelines to ensure accurate, reproducible results. Most markers are sensitive to recent food, exercise, and sleep.
Can't find your answer? Our clinical support team is available Monday to Friday, 9am–5pm.
Contact supportInadequate dietary intake is the most common root cause; magnesium is abundant in green leafy vegetables, nuts, seeds, and wholegrains, but these foods are frequently under-consumed in typical Western diets. Medications that increase urinary magnesium loss include diuretics (furosemide, thiazides), proton pump inhibitors with long-term use, and some chemotherapy agents. Medical conditions associated with magnesium depletion include type 2 diabetes (insulin resistance increases renal magnesium excretion), inflammatory bowel disease, coeliac disease, and alcohol dependency. Chronic psychological stress increases urinary magnesium excretion and depletes cellular stores further.
Magnesium supplementation is generally effective, but the form matters for tolerability and absorption. Magnesium oxide is poorly absorbed and commonly causes diarrhoea at doses needed to meaningfully raise levels. Better-absorbed and better-tolerated forms include magnesium glycinate (glycine chelate, also promotes sleep), magnesium malate (good for energy and muscle pain), magnesium threonate (studied for cognitive function), and magnesium citrate (widely available and reasonably well absorbed). Avoid oxide as a primary form. Topical magnesium (sprays, creams, bath flakes) has some evidence but the transdermal absorption is variable.
Yes. Magnesium plays a critical role in cardiac electrophysiology, particularly in regulating sodium and potassium channels in cardiac muscle cells. Low magnesium is associated with increased cardiac excitability, which can manifest as ectopic beats (a common cause of the fluttering or skipping sensation described as palpitations), and in more severe cases with more significant arrhythmias. This is why magnesium is used intravenously in hospital settings for certain life-threatening arrhythmias. If you are experiencing palpitations, a simple serum magnesium check is a reasonable first investigation alongside an ECG.
Yes, through two related mechanisms. First, acute psychological stress triggers release of adrenaline, which promotes urinary magnesium excretion as part of the fight-or-flight response. Second, stress increases cortisol, and chronically elevated cortisol further enhances renal magnesium loss. This creates a problematic cycle: low magnesium increases nervous system reactivity, which increases perceived stress, which further depletes magnesium. Addressing magnesium status is therefore a reasonable part of a broader approach to stress resilience, alongside sleep, exercise, and psychological support.
Hypermagnesaemia (dangerously elevated magnesium) from oral supplements is very rare in people with normal kidney function because the kidneys efficiently excrete excess magnesium. At high doses, the main adverse effect is diarrhoea due to the osmotic effect of unabsorbed magnesium in the intestine — this is actually the mechanism exploited by magnesium-based laxatives. However, in individuals with renal impairment, magnesium can accumulate to dangerous levels; caution and medical supervision are warranted in this group. Standard supplement doses of 200 to 400 mg daily are well within safe limits for most adults.
