Can dehydration cause high blood pressure?

No.: It causes low blood pressure as per Advanced Cardiac Life Support certification training.

Rarely: In rare cases, I have seen a patient with dehydration have high blood pressure. This occurs presumably because the body's response is to "clamp down" (vasoconstrict). Interestingly, in these patients, restoring the volume with IV fluids led to the blood pressure coming back down to normal.