Differential Diagnosis for Low Blood Pressure Only in the Morning

• Single Most Likely Diagnosis
  • Orthostatic hypotension due to overnight fasting and dehydration: This condition occurs when blood pressure drops upon standing, often due to dehydration or decreased blood volume, which can be exacerbated by overnight fasting and increased urine production during sleep.
• Other Likely Diagnoses
  • Postural orthostatic tachycardia syndrome (POTS): Characterized by a rapid increase in heart rate and other symptoms upon standing, which can include morning low blood pressure due to autonomic nervous system dysfunction.
  • Autonomic dysfunction: Conditions affecting the autonomic nervous system, such as diabetes or certain neurological disorders, can lead to abnormal blood pressure regulation, particularly noticeable in the morning.
  • Medication side effects: Certain medications, especially those used to treat hypertension or heart conditions, can cause hypotension, particularly if their effects peak in the morning.
• Do Not Miss Diagnoses
  • Adrenal insufficiency: A life-threatening condition where the adrenal glands do not produce enough cortisol and aldosterone, leading to hypotension, which can be more pronounced in the morning due to the natural circadian rhythm of cortisol.
  • Pheochromocytoma: Although typically associated with hypertension, some patients with pheochromocytoma can experience orthostatic hypotension, particularly in the morning, due to the intermittent nature of catecholamine release.
• Rare Diagnoses
  • Dysautonomia: A rare disorder of the autonomic nervous system that can cause a wide range of symptoms, including abnormal blood pressure regulation, which might be more noticeable in the morning.
  • Baroreflex failure: A rare condition where the body's baroreflexes, which help regulate blood pressure, are impaired, leading to labile blood pressure, which could manifest as morning hypotension.