Dehydration: This is often the most common cause of orthostatic hypotension, especially in patients who have been experiencing vomiting, diarrhea, or excessive sweating, leading to a significant loss of fluids and electrolytes.

Medication Side Effects: Certain medications such as diuretics, beta-blockers, and certain antidepressants can cause orthostatic hypotension as a side effect by either reducing blood volume or affecting the body's ability to regulate blood pressure.
Autonomic Dysfunction: Conditions that affect the autonomic nervous system, such as diabetes, can lead to orthostatic hypotension due to impaired sympathetic and parasympathetic responses.
Anemia: A decrease in red blood cells or hemoglobin can reduce the body's ability to transport oxygen, leading to feelings of faintness and orthostatic hypotension.

Cardiac Conditions: Conditions such as heart failure, significant valvular disease, or cardiac tamponade can lead to orthostatic hypotension due to reduced cardiac output. Missing these diagnoses could be fatal.
Bleeding or Hemorrhage: Internal bleeding can cause significant blood loss, leading to orthostatic hypotension. Early detection is crucial for survival.
Adrenal Insufficiency: This condition, where the adrenal glands do not produce adequate amounts of hormones, can lead to orthostatic hypotension among other symptoms. It is critical to diagnose and treat promptly to avoid adrenal crisis.

Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodes of high blood pressure but also orthostatic hypotension due to its unpredictable effects on blood pressure regulation.
Multiple System Atrophy (MSA): A rare neurodegenerative disorder that affects adult men and women, characterized by autonomic dysfunction, including orthostatic hypotension.
Pure Autonomic Failure (PAF): A rare condition characterized by progressive autonomic dysfunction, leading to severe orthostatic hypotension without other significant neurological features.