Dehydration: This is often the most common cause of hypotension in elderly patients due to decreased fluid intake, excessive fluid loss (e.g., diarrhea, vomiting), or medications that increase urine output (e.g., diuretics).

Medication Side Effects: Many medications can cause hypotension, including antihypertensives, beta-blockers, and certain antidepressants. Elderly patients are more susceptible due to polypharmacy and age-related changes in drug metabolism.
Autonomic Dysfunction: Conditions like diabetes, Parkinson's disease, or multiple system atrophy can lead to autonomic nervous system failure, resulting in orthostatic hypotension.
Heart Failure: Reduced cardiac output can cause persistent low blood pressure. This could be due to systolic or diastolic dysfunction, often a result of long-standing hypertension, coronary artery disease, or cardiomyopathy.
Anemia: Severe anemia can lead to a decrease in blood pressure due to reduced oxygen delivery to tissues, prompting a compensatory increase in cardiac output, which may not always be sufficient.

Septic Shock: Although less common in the absence of obvious infection signs, septic shock can present with hypotension and must be considered, especially in elderly patients who may not exhibit typical symptoms of infection.
Hemorrhage: Internal or external bleeding can cause hypotension. Elderly patients might not always show typical signs of hemorrhage, making it a critical diagnosis not to miss.
Adrenal Insufficiency: This condition, including Addison's disease, can cause hypotension due to the lack of cortisol and aldosterone production. It's crucial to consider, especially if the patient has a history of steroid use or autoimmune disorders.
Neurogenic Shock: Spinal cord injury or severe neurological conditions can lead to loss of sympathetic tone, resulting in hypotension.

Pheochromocytoma: Although typically associated with hypertension, a rare presentation of pheochromocytoma can cause persistent hypotension, especially if there's significant alpha-adrenergic blockade or if the tumor secretes certain vasoactive substances that predominantly cause vasodilation.
Amyloidosis: Systemic amyloidosis can infiltrate the heart, leading to restrictive cardiomyopathy and hypotension.
Vitamin B12 Deficiency: Severe vitamin B12 deficiency can lead to neurological and hematological manifestations, including orthostatic hypotension due to autonomic dysfunction.