Low potassium can also cause muscle cramps (i.e., charley horses)
Could be a lack of Magnesium! Your physician can check your Magnesium levels with a blood test. I have a friend having same issues and she is taking additional Mag.
Usually it is lack of calcium, and a glass or two of milk every day solves the problem. Sometimes lack of magnesium. Vitamin D3 is necessary for calcium uptake so a check on D3 levels is in order and a supplement or more skin exposure to sunlight. Sunlight exposure doesn't always work. I get lots of such exposure and test for non-existent D3 (go figure), so I have to take supplements. Otherwise my hands "cramp".