In simple terms
Hypotension is the medical term for low blood pressure. It means blood is moving through the vessels at a lower pressure than usual.
The US National Heart, Lung, and Blood Institute puts the line at a reading below 90/60 mmHg, against a normal adult figure usually below 120/80 mmHg.
How it works
Unlike high blood pressure, a low reading is not treated as a problem on its own. What matters is whether too little blood is reaching the brain and other organs, which is what produces symptoms.
Reported symptoms include dizziness, lightheadedness, fainting, blurry vision, confusion, fatigue, headaches, nausea and heart palpitations. Many people with a low reading have none of them.
One form is defined precisely. Orthostatic hypotension is a sustained fall of at least 20 mmHg systolic, or 10 mmHg diastolic, within three minutes of standing up. It becomes more common with age: under 5 percent of people aged 45 to 49, about 15 percent at 65 to 69, and more than 25 percent at 85 and older.
Causes are wide ranging. They include blood loss, dehydration, pregnancy, heart rhythm problems and diabetes, as well as medicines taken for blood pressure, depression or Parkinson’s disease.
Why it matters
Fainting and falls are the everyday risk, and they matter most for older people, for whom a fall can have serious consequences.
A very low pressure can also be a sign of shock, which is a medical emergency. The NHLBI lists cold and sweaty skin, rapid breathing, a blue skin tone, or a weak and rapid pulse as signs of shock, and says to call emergency services if they appear.
Where you’ll see it
- Blood pressure readings taken at clinics and pharmacies.
- Medicine labels warning that a drug can lower blood pressure.
- Fall prevention guidance for older adults.
Example
A reading of 85/55 mmHg sits below the NHLBI threshold for low blood pressure.
Often confused with
Hypertension. The two words look alike and mean opposites. Hypertension is blood pressure that is too high.
Key facts
- NHLBI defines low blood pressure as blood pressure lower than 90/60 mmHg, compared with a normal adult reading usually less than 120/80 mmHg.1
- Symptoms listed by NHLBI include confusion, dizziness, lightheadedness, fainting, fatigue, blurry vision, headaches, neck or back pain, nausea and heart palpitations.1
- NHLBI lists causes and risk factors including blood loss, dehydration, diabetes, heart arrhythmias, pregnancy, and medicines for blood pressure, depression or Parkinson's disease; older adults are at higher risk of symptomatic episodes.1
- NHLBI lists signs of shock as cold and sweaty skin, rapid breathing, a blue skin tone, or a weak and rapid pulse, and advises calling emergency services if they appear.1
- Orthostatic hypotension is defined as a sustained drop of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing.2
- Prevalence of orthostatic hypotension rises with age in US population studies: under 5 percent at ages 45 to 49, about 15 percent at 65 to 69, and over 25 percent at 85 and older.2
This entry explains a medical term. It is not medical advice. If you are concerned about your health, speak with a qualified health professional.
Go deeperWhy Do You Feel Dizzy When You Stand Up Too Fast?Related concepts
In the news
Quick checkWhat reading does the NHLBI treat as low blood pressure?Show answer
Below 90/60 mmHg, against a normal adult reading usually under 120/80 mmHg.
Sources
- National Heart, Lung, and Blood Institute, NIH. Low Blood Pressure. 24 March 2022 (last updated) (accessed 14 September 2026)
- StatPearls, NCBI Bookshelf, National Library of Medicine. Orthostatic Hypotension. Undated (accessed 14 September 2026)
Editorially reviewed by Specialty Digest Editorial TeamLast reviewed September 17, 2026Researched and drafted with AI assistanceReport an issue