HELP FOR PAINFUL LEG CRAMPS. Painful cramps in your legs, calves and feet can interrupt your sleep. In most cases, leg cramps can be attributed to a magnesium deficiency. Leg Cramp Relief contains 400 mg magnesium plus potassium which supports proper muscle function. This fast-absorbing formula starts working immediately to ease painful cramps, with increased benefits over time. 90 capsules (45-day supply).