Magnesium for migraine: dose, form and evidence

What did the migraine trials find?

The positive German trial. In 1996, Peikert and colleagues gave 81 adults with migraine either 600 mg of magnesium a day (as trimagnesium dicitrate) or placebo for 12 weeks. In the final month, attacks were 41.6% less frequent than at the start in the magnesium group, against 15.8% in the placebo group. Migraine days and painkiller use also fell. The main side effect was diarrhoea, in almost one in five people.

The negative German trial. In the same year, Pfaffenrath and colleagues tested magnesium aspartate in 69 people. Ten people in each group responded, so magnesium did no better than placebo, and the trial was stopped early.

The meta-analysis. A 2016 review combined 10 trials of oral magnesium for migraine prevention, involving 789 people, and found it reduced both how often attacks came and how bad they were. Some of the trials were not well randomised, which weakens the result.

Menstrual migraine. A small Italian trial in 1991 gave 20 women with migraines linked to their periods 360 mg of magnesium a day, or placebo, from mid-cycle until their next period. After two months, the magnesium group had fewer headache days and lower pain scores, and their premenstrual symptoms improved. It was very small, but it’s one reason some doctors suggest magnesium for this type of migraine.

Children. A 2003 trial of magnesium oxide in 118 children aged 3 to 17 found lower headache severity, but the fall in headache frequency was not clearly different from placebo.

What do guidelines say?

The 2012 American Academy of Neurology and American Headache Society guideline rated magnesium as “probably effective” for preventing migraine, its second-highest level. UK guidance concentrates on prescribed preventers, so ask your GP whether magnesium is worth trying alongside or instead of them.

How would you take magnesium for migraine?

• The trials used around 600 mg of elemental magnesium a day, split into two or three doses with food. The positive trial used magnesium citrate.
• That is above the NHS’s 400 mg comfort level for supplements. Discuss it with your GP or pharmacist first, and don’t take it if you have kidney disease unless your doctor advises you to.
• Start lower, for example 200 mg twice a day, and build up to limit diarrhoea. See side effects and dosage and timing.
• Check medicines it affects if you take other regular medicines.
• Keep a headache diary for a month before and three months during, so you can tell whether it is working.

What doesn’t the evidence show?

The trials are small and old, and one large one was negative. There are no long-term studies. Magnesium has not been tested head-to-head against prescribed preventers such as propranolol, amitriptyline or topiramate, so we cannot say how it compares. If your migraines are frequent or changing, see your GP.