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Q: I get these brutal leg cramps at night that wake me from sleep. I can never predict when and why they happen. Are there ways to prevent them? 

A: Leg cramps are muscle spasms that happen when nerves that power muscle contractions go into a nonstop firing mode. 

They are more common among people with foot problems like flat feet or high arches, metabolic disorders, or neurological conditions such as Parkinson’s disease or neuropathy (nerve damage).  

Dehydration and electrolyte imbalances, such as low blood potassium or magnesium levels (a common side effect of diuretics), can increase the risk of cramping. However, many people with recurrent leg cramps cannot identify a cause. 

How to stop one in progress 

To stop a foot or leg cramp once it happens, stand up and slowly lean forward. If you don’t want to get out of bed, sit up and reach forward so you can grab your toes, then slowly bend your foot up toward your head. Hold for about 20 seconds, then release. Repeat as needed. 

Despite the lack of scientifically proven ways to prevent recurrent nighttime leg cramps, a few approaches may be worth trying. 

Begin with stretching exercises. While facing a wall and standing about two feet away, lean forward until your hands touch the wall. Keep your legs straight and feet flat on the floor.  

You should feel a stretch, but it should not be painful. Hold the position for 20 seconds and release. 

Repeat the stretch four to five times. Try to do this three times per day for at least the first few weeks and then as needed. The most important time to stretch is before bedtime. 

Other preventive measures include staying well hydrated, wearing well-fitting supportive footwear during the day, and keeping the bedding at your feet loose during the night. 

Although the evidence isn’t strong, some people find that taking a daily B-complex vitamin supplement containing eight B vitamins — B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6, B7 (biotin), B9 (folate), and B12 — helps prevent cramps. 

Quinine is one drug known to be effective in reducing the frequency of muscle cramps. However, the drug is out-of-bounds for most people.  

Quinine has FDA approval to treat certain types of malaria. But the FDA has issued repeated warnings against using quinine to prevent or treat leg cramps because it may cause serious side effects, including severe anemia, bleeding and kidney damage.  

Although doctors can still prescribe quinine, it is recommended only when cramps are disabling and the person understands the significant risks. 

Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, see health.harvard.edu. 

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