Can Magnesium Ease Nighttime Leg Cramps?

Medically Reviewed

If leg cramps are keeping you up at night, can a magnesium supplement help you rest easier? Researchers in Israel studied a group of older adults who had frequent nighttime leg cramps (four or more times over two weeks) to find out.

Volunteers were given either a magnesium oxide supplement or a placebo pill to take at bedtime. Nighttime leg cramp episodes and their severity were recorded over four weeks.

Among the 94 patients who completed the study (average age of 65), the researchers found little difference in incidence or severity between the magnesium pills and the dummy pills. The researchers, whose findings were published online in February 2017 in JAMA Internal Medicine , concluded that magnesium oxide is ineffective for nighttime leg cramps.

Sudden pain at night

Nighttime leg cramps are painful muscle contractions that come on without warning and can occur several times a week. Many people turn to over-the-counter magnesium supplements for relief, but studies gauging the effectiveness of those supplements have been inconclusive.

The JAMA Internal Medicine study had its flaws as well. Magnesium oxide capsules must be taken with a full glass of water or the preparation won’t be adequately absorbed into the bloodstream, says Edward Blonz, Ph.D., an assistant professor in the department of clinical pharmacy at the University of California, San Francisco.

The researchers did not indicate whether they instructed people to drink enough water with the supplement or if blood or urine tests were performed to measure magnesium levels.

"I am disappointed that those issues were not raised,” Blonz says, adding that other magnesium preparations such as citrate, aspartate, lactate, and chloride are absorbed more thoroughly and may be more effective.

Supplemental magnesium

Magnesium offers many other health benefits, including muscle relaxation when combined with calcium, Blonz says.

For older people, or anyone not eating a balanced diet, a basic multivitamin/mineral is a good way to get supplemental magnesium (usually 50 to 100 milligrams). Some calcium supplements also contain magnesium.

You can’t get too much magnesium from food. Some good sources are halibut, sunflower seeds, spinach, and almonds. In contrast, supplements and excessive use of certain magnesium-containing antacids or laxatives can cause diarrhea, nausea and cramps. People with kidney disease are at risk for more serious problems from excess magnesium.

Help for leg cramps

If you suffer from nighttime leg cramps, the following tips may help you prevent them:

Wear comfortable shoes with low heels.

Do exercises that strengthen your calf muscles, such as toe raises.

Massage and stretch your calf muscles, especially at bedtime.

If you sleep on your back, keep the sheets and blankets loose so that they don't press down on your feet and cause cramping.

If you get a cramp, massage the calf muscles and stretch them by pulling your toes up toward your knee and walking around.

Here are some other tips to try for nighttime leg cramps.