My wife gets cramps in her left calf. What is this cause from?

Cramps in calf. Check potassium ,magnesium , calcium , Vit D, sodium level. if she is a runner when drinking drink 1/2 water 1/2 gatorade juice so you do not dilute sodium or check for blood clot especially if on BCP or smoker. F/U with doctor/urgent care today to insure not clot.