7 Answers

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 a low potassium level  could do  this. You would have to see a dr to get blood level drawn. Being inactive.

Ditto on blood work up to have potassium level checked.

Assume it is a potassium problem. Eat a banana before you go to bed. Keep eating them until you get checked by a doctor...............

Just today I learned that a possible side effect of the drug Simvastatin can be cramping. Check with your doctor if taking a "statin" drug. 

You're low on magnisium and maybe potassium too. One thing most Americans is low on is Vit D. Try walking everyday . And consume a lot of dairy products

It could be a number of problems, potassium being one of them. Although, potassium can be a very ticky thing to regulate. Too low or too high and you are in danger which affects your heart. Don't eat any banans until you get a blood draw done. It doesn't take much to put your levels off. Never self-diagnois, please seek professional help.