Magnesium is a popular supplement for improving sleep, but it may also help lower blood pressure. Although there’s no single ideal time to take it, other factors may influence how effectively it supports blood pressure.
Scientists are still learning how magnesium supplements affect blood pressure. So far, results are most promising for people with abnormally high blood pressure who are deficient in the mineral, said Jocelyn Edwards, Pharm.D, a clinical assistant professor of cardiology at the University of Maryland School of Pharmacy.
A 2025 review of 38 randomized controlled trials found that magnesium was more effective than a placebo at lowering blood pressure in people with hypertension or magnesium-related electrolyte imbalances. Notably, however, there was no statistically significant reduction in those with normal blood pressure or magnesium levels.
Even for groups that may see greater benefit, experts said there is no one best time to take magnesium. “In general, magnesium supplements can be taken at any time in the day,” Edwards said. “The best time of day,” she added, “is ultimately whatever allows the patient to take their medication conveniently and consistently.”
There are several potential ways magnesium may affect blood pressure. First, it reduces inflammation. It also helps blood vessels relax and widen by stimulating their inner lining to release prostaglandins and nitric oxide, Edwards said.
Magnesium also acts as a calcium blocker. “When calcium enters the cells of blood vessels, it causes them to constrict, which increases pressure,” Edwards said. “Inhibition of this process results in relaxation of the blood vessels and reduction of blood pressure.”
While timing may not play a role in how well magnesium works, other factors can. Certain medications, such as proton pump inhibitors, can decrease the absorption of magnesium, as can taking high doses of calcium, zinc, or iron at the same time. That’s why it’s best to take these drugs or supplements at least two hours before or after your magnesium supplement, according to experts.
It’s also “important to consult with your healthcare provider or pharmacist before starting magnesium if you are on other medications,” Edwards said.
Meanwhile, some vitamins—namely, D, C, and B6—may improve the absorption of magnesium, Edwards pointed out.
When it comes to the type of magnesium to take, research has not yet determined whether one form, such as organic compounds like magnesium citrate and glycinate, works best for blood pressure support. “There is not yet sufficient data to determine if any one formulation produces a more significant blood pressure–lowering effect,” Edwards said. “Any formulation that can be tolerated and taken consistently by the patient is reasonable to use for this purpose.”
Regardless, experts agree that it’s best to try to get magnesium through food rather than supplements. Magnesium-rich foods include leafy greens, avocados, bananas, legumes, whole grains, and nuts. “Incorporating these into your diet regularly can help to increase levels,” Edwards said.
