There are several possible causes of an overnight calf cramp, says a pain doctor.

Many people have suffered from the sudden spasm of a calf muscle in the middle of the night, caused by tensing it a bit too much while stretching. This pain is excruciating but is not a serious condition.

But what if the calf pain occurs in the absence of some careless stretching of a muscle that’s been stiffened by several hours of sleep? This problem can occur even to physically fit people.

“Typically cramps in an athlete are caused by decreased circulation with oxygen after prolonged activity,” says Dr. Moshe Lewis, MD, Chief of Physical Medicine andRehabilitation at California Pacific Medical Center – St. Luke’s Campus in the Department of Orthopedics.

“This phenomenon can also be seen in diabetics and smokers who also have poor circulation for different reasons. Classically these two groups of patients also have pain when they walk called claudication.”

What are some other causes of calf pain or cramps overnight? Dr. Lewis says, “In the non-athlete or someone who has not had prolonged activity that day, night cramps are due to sciatica. When nerves get pinched or impinged, positional changes at night can cause muscles to go into spasm. This occurs because nerves send key information to muscles which lets them work correctly. When those signals are disrupted muscles spasm.”

There are still yet other variables that can cause calf pain or cramping in the middle of the night, though these other causes can also cause symptoms during the day. They are vasculitis, phlebitis, a herniated lumbar disc, potassium deficiency and DVT.

DVT, or deep vein thrombosis, is a blood clot that requires immediate medical attention, as it can dislodge and travel to the lungs, causing a fatal pulmonary embolism.