Which magnesium is best for migraines is a common question for those seeking natural preventive options. Magnesium supplementation may help reduce migraine frequency through its effects on neurological function and vascular regulation. Several forms are available in the UK, including magnesium citrate, magnesium oxide, and magnesium glycinate, each with different absorption rates and tolerability profiles. Whilst clinical evidence supports magnesium as 'probably effective' for migraine prevention, no single form has been definitively proven superior. This article examines the different types of magnesium supplements, recommended dosages, safety considerations, and when to seek medical advice for migraine management.

How Magnesium Helps Prevent Migraines

Magnesium plays a crucial role in neurological function and vascular regulation, both of which are implicated in migraine pathophysiology. Research suggests that individuals who experience migraines may have lower magnesium levels compared to those without the condition, though the exact relationship remains an area of ongoing investigation.

The mineral may contribute to migraine prevention through several proposed mechanisms. Magnesium is thought to act as a natural calcium channel blocker, potentially helping to regulate neurotransmitter release and prevent the excessive neuronal excitation associated with migraine attacks. It may also influence the release of substance P and other neuropeptides involved in pain transmission. Additionally, magnesium helps maintain normal vascular tone and might affect cortical spreading depression—a wave of electrical activity across the brain—that is hypothesised to trigger migraine aura.

Clinical evidence supporting magnesium supplementation for migraine prevention has been examined in multiple studies. A Cochrane systematic review found that magnesium supplementation may reduce migraine frequency in some patients, though the quality of evidence is moderate to low. The American Academy of Neurology and American Headache Society have classified magnesium as "probably effective" for migraine prevention (Level B evidence). In the UK, the British Association for the Study of Headache (BASH) acknowledges magnesium as a potential option, though it is not routinely recommended in NICE guidelines for migraine prevention.

It is important to note that magnesium supplementation works best as a preventive measure rather than an acute treatment for active migraine attacks. Patients typically need to take magnesium consistently for several weeks before noticing any reduction in migraine frequency or severity. Those considering magnesium supplementation should discuss this option with their GP or headache specialist, particularly if they are taking other medications or have underlying health conditions.

Types of Magnesium Supplements Available in the UK

Several forms of magnesium supplements are available in UK pharmacies and health food shops, each with different properties. Understanding these differences may help when selecting a supplement for migraine prevention.

Magnesium oxide is one of the most commonly available and affordable forms. It contains a high percentage of elemental magnesium by weight (approximately 60%), but has relatively low absorption rates—meaning the body absorbs only a small proportion of the magnesium content. Despite this limitation, magnesium oxide has been used in some clinical trials for migraine prevention and may still provide benefit, though it is more likely to cause gastrointestinal side effects.

Magnesium citrate offers better absorption than magnesium oxide and is generally well-tolerated. This form combines magnesium with citric acid, creating a compound that dissolves readily in water and is more easily absorbed in the digestive tract. It contains approximately 16% elemental magnesium and has a mild laxative effect, which can be beneficial for those with constipation but may be problematic for others.

Magnesium glycinate (also called magnesium bisglycinate) is bound to the amino acid glycine, which may improve tolerability, particularly for those with sensitive digestive systems. This form typically causes fewer gastrointestinal side effects than magnesium oxide.

Other forms available in the UK include magnesium malate (combined with malic acid), magnesium taurate (bound to the amino acid taurine), and magnesium threonate. Topical magnesium preparations, such as oils and bath salts containing magnesium chloride, are also popular, though evidence for their effectiveness in migraine prevention is very limited compared to oral supplementation.

When choosing a supplement, it's important to check the label for the amount of elemental magnesium per dose, as this varies considerably between different magnesium compounds. The UK safe upper level for supplemental magnesium is 400 mg per day (in addition to dietary intake) according to Expert Group on Vitamins and Minerals guidance.

Which Magnesium Is Best for Migraines

When selecting a magnesium supplement specifically for migraine prevention, several factors should be considered, including absorption, tolerability, and the evidence supporting its use.

Magnesium citrate has been used in clinical trials for migraine prevention. For example, a placebo-controlled study by Peikert et al. (1996) used 600 mg of trimagnesium dicitrate (providing approximately 100 mg of elemental magnesium) and found a reduction in migraine frequency. Its relatively good absorption and tolerability make it a practical option for many people.

Magnesium oxide has also been studied for migraine prevention. While it has lower absorption rates, the higher elemental magnesium content means that even with reduced absorption, a therapeutic amount may still reach the bloodstream. However, gastrointestinal side effects—particularly diarrhoea—are more common with this form, which may affect adherence to treatment.

Magnesium glycinate may be better tolerated by those who experience digestive upset with other forms. Its structure may reduce gastrointestinal side effects and minimise laxative effects. While there are fewer large-scale trials specifically using magnesium glycinate for migraines, its tolerability profile makes it a practical choice for some individuals.

The clinical evidence does not definitively establish that any one form of magnesium is superior to others specifically for migraine prevention. Individual factors such as tolerability, cost, and convenience may be more important considerations. Some people may need to try different forms to find one that suits them best.

When choosing a supplement, focus on the elemental magnesium content rather than the total weight of the compound. UK supplements should clearly state the elemental magnesium content per dose and the percentage of Nutrient Reference Value (NRV), which is 375 mg for magnesium in the UK.

Recommended Dosage and How to Take Magnesium for Migraines

The dosage of magnesium for migraine prevention has been investigated in various clinical studies, with most research supporting daily doses between 300–400 mg of elemental magnesium. It is essential to distinguish between the total weight of the magnesium compound and the amount of elemental magnesium it contains, as supplement labels may list either figure.

For context, the UK Reference Nutrient Intake (RNI) for magnesium is 300 mg for men and 270 mg for women daily from all sources. The Nutrient Reference Value (NRV) used on UK supplement labels is 375 mg. The Expert Group on Vitamins and Minerals has established a safe upper level for supplemental magnesium of 400 mg per day (in addition to dietary intake).

Timing and administration can influence both efficacy and tolerability. Magnesium supplements are generally best taken with food to enhance absorption and reduce gastrointestinal side effects. Dividing the daily dose—for example, taking 150-200 mg twice daily rather than 300-400 mg once—may further improve tolerability. Some people find taking magnesium in the evening helpful, as it may have mild relaxing properties.

Patients should understand that magnesium supplementation for migraine prevention requires consistent, long-term use. Benefits typically emerge after 4–12 weeks of regular supplementation, so patience and adherence are essential. It is not effective as an acute treatment during a migraine attack.

Magnesium can interact with certain medications. It should be taken at least 4 hours apart from levothyroxine, iron supplements, and some antibiotics (particularly tetracyclines and fluoroquinolones) and bisphosphonates. Always follow the specific spacing advice on medication patient information leaflets or consult a pharmacist.

Before starting supplementation, individuals should consult their GP or pharmacist, particularly if they have kidney disease, heart conditions, or are taking medications that may interact with magnesium. Blood tests to assess magnesium levels are not routinely necessary, as serum magnesium does not accurately reflect total body stores, but may be considered in specific clinical situations.

Potential Side Effects and Safety Considerations

Magnesium supplementation is generally considered safe for most individuals when taken at recommended doses, but certain side effects and contraindications warrant attention. Understanding these considerations helps ensure safe and effective use for migraine prevention.

Gastrointestinal effects are the most common side effects associated with magnesium supplementation. These include diarrhoea, nausea, abdominal cramping, and bloating. The severity of these effects varies considerably depending on the form of magnesium used, with magnesium oxide being most likely to cause loose stools due to its laxative properties. Starting with a lower dose and gradually increasing, choosing a form that you tolerate better, or dividing the daily dose can help minimise these effects. If persistent diarrhoea occurs, reduce the dose or discontinue use and consult a healthcare professional.

Hypermagnesaemia (excessively high magnesium levels) is rare in individuals with normal kidney function, as the kidneys efficiently excrete excess magnesium. However, patients with chronic kidney disease or renal impairment should exercise caution and consult their nephrologist before taking magnesium supplements, as they are at increased risk of magnesium accumulation. Symptoms of hypermagnesaemia include muscle weakness, hypotension, cardiac arrhythmias, and in severe cases, respiratory depression.

Magnesium can interact with several medications. It may reduce the absorption of certain antibiotics (particularly tetracyclines and fluoroquinolones), bisphosphonates used for osteoporosis, levothyroxine, and iron supplements. Patients taking these medications should separate doses by at least 4 hours, or as directed in the medication patient information leaflet. Magnesium may potentially affect the action of some blood pressure medications and muscle relaxants.

Individuals with myasthenia gravis should avoid magnesium supplementation, as it can worsen muscle weakness. Those with heart block or other cardiac conduction disorders should also seek medical advice before supplementing.

Pregnant and breastfeeding women considering magnesium supplementation for migraine prevention should discuss this with their midwife or GP, as dosing recommendations may differ. Whilst magnesium is essential during pregnancy, supplementation should be appropriately supervised.

Magnesium supplements are food supplements, not licensed medicines for migraine prevention in the UK. If you experience any suspected adverse reactions, report them through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

When to Seek Medical Advice About Migraines

Whilst magnesium supplementation may help reduce migraine frequency for some individuals, it is crucial to recognise when professional medical evaluation is necessary. Certain migraine presentations and associated symptoms require urgent or specialist assessment.

Immediate medical attention (via 999 or A&E) is warranted if a headache is accompanied by: sudden onset of the worst headache ever experienced ("thunderclap headache"), fever with neck stiffness, confusion or altered consciousness, seizures, weakness or numbness on one side of the body, visual disturbances that differ from typical migraine aura, or difficulty speaking. These symptoms may indicate serious conditions such as subarachnoid haemorrhage, meningitis, or stroke, which require emergency investigation. Additional red flags include headache following head injury, new headache in someone with cancer or who is immunosuppressed, or severe headache during pregnancy or postpartum.

Patients should contact their GP if they experience: a significant change in their usual migraine pattern, headaches that are increasing in frequency or severity despite self-management strategies, migraines that do not respond to over-the-counter medications, or headaches that significantly impact daily functioning and quality of life. Additionally, individuals experiencing their first migraine after age 50, or those with new-onset aura symptoms, should be evaluated to exclude secondary causes.

Referral to a specialist (typically a neurologist or headache specialist) may be appropriate for patients with chronic migraine (15 or more headache days per month), those who have not responded to multiple preventive treatments, or individuals with complex or atypical presentations. NICE guidelines recommend considering specialist referral when diagnosis is uncertain or when management in primary care has been unsuccessful.

Before starting magnesium supplementation, patients should discuss this with their GP, particularly if they have underlying health conditions, take regular medications, or are pregnant. A healthcare professional can help determine whether magnesium supplementation is appropriate, advise on suitable dosing, and ensure it is integrated safely within a comprehensive migraine management plan that may include lifestyle modifications, trigger avoidance, and other evidence-based preventive strategies. Regular follow-up allows for monitoring of treatment response and adjustment of the management approach as needed.

Frequently Asked Questions