When the blood pressure is too low, there is inadequate blood flow to the heart, brain, and other vital organs.

A blood pressure level that is borderline low for one person may be normal for another. The most important factor is how the blood pressure changes from the normal condition. Most normal blood pressures fall in the range of 90/60 mm Hg to 130/80 mm Hg, but a significant change, even as little as 20 mm Hg, can cause problems for some people.

Low blood pressure is commonly caused by drugs such as the following

• Medications used for surgery
• Anti-anxiety agents
• Treatment for high blood pressure
• Diuretics
• Heart medicines
• Some antidepressants
• Narcotic analgesics
• Alcohol

Other causes of low blood pressure include the following:

• Dehydration
• Heart failure
• Heart attack
• Changes in heart rhythm (arrhythmias)
• Syncope
• Anaphylaxis (a life-threatening allergic response)
• Shock (from severe infection, stroke, anaphylaxis, major trauma, or heart attack)
• Advanced diabetes

Another common cause type of low blood pressure is orthostatic hypotension, which results from a sudden change in body position, usually from lying down to an upright position.

• Call your health care provider if there is any sudden drop in blood pressure that causes dizziness or fainting spells. Call an ambulance and begin CPR if someone is unconscious.
• You notice black or maroon stools
• You experience any of the following:
  • Chest pain
  • Shortness of breath
  • Palpitations
  • Fever higher than 101 degrees
  • Headache
  • Stiff neck
  • Severe upper back pain
  • Cough with phlegm
  • Prolonged diarrhea or vomiting
  • Inability to eat or drink
  • Burning with urination
  • Foul-smelling urine
• Your low blood pressure or dizziness/fainting spells started one or two days after you began taking a new drug.

In emergencies, the seriousness of the condition will be determined first. Then, the health care provider will obtain your medical history and will perform a physical examination.

Frequent monitoring of vital signs (temperature, pulse, rate of breathing, blood pressure) and/or hospitalization may be necessary.

Medical history questions documenting low blood pressure may include the following:

• What is your normal blood pressure?
• What medications do you take?
• Have you been eating and drinking normally?
• Have you have any recent illness, accident, or injury?
• What other symptoms are also present?
• Did you faint or become less alert?
• Do you feel dizzy or light-headed when standing or sitting after lying down?

• Blood studies (such as CBC, blood differential)
• Cultures
• ECG
• Urinalysis
• X-ray of the abdomen
• X-ray of the chest