down. Orthostatic hypotension can cause dizziness or lightheadedness and possibly fainting. Orthostatic hypotension can be mild. Episodes might be brief. However, long-lasting orthostatic hypotension can signal more-serious problems. It's important to see a health care provider if you frequently feel lightheaded when standing up. Occasional orthostatic hypotension is usually caused by something obvious, such as dehydration or lengthy bed rest. The condition is easily treated. Chronic orthostatic hypotension is usually a sign of another health problem, so treatment depends on the cause.