Causes of Low Blood Pressure

Low blood pressure can be a lifelong individual trait with no underlying cause, or it can result from a specific, sometimes temporary, factor.

Common Causes

• Dehydration — even mild fluid loss reduces blood volume, lowering pressure
• Medications — certain blood pressure medications (especially if the dose is too high), diuretics, and some medications for depression or Parkinson's disease can lower blood pressure
• Prolonged bed rest — reduces the body's ability to regulate pressure changes
• Pregnancy — blood pressure often drops somewhat, particularly in the first half of pregnancy
• Heart conditions — including slow heart rate, heart valve problems, and heart failure
• Endocrine conditions — including thyroid problems and adrenal gland disorders
• Severe infection or significant blood loss — these cause a sudden, dangerous drop and are medical emergencies

When Position Matters: Orthostatic Hypotension

Some people experience a sudden drop in blood pressure specifically when standing up from sitting or lying down, causing brief dizziness or lightheadedness. This is common, especially with age, dehydration, or certain medications.

After-Meal Drops: Postprandial Hypotension

Blood pressure can also drop after eating, as blood flow shifts toward the digestive system — a pattern called postprandial hypotension. It's most common in older adults and can cause the same dizziness or lightheadedness as other forms of low blood pressure.