- 01The number matters less than what it does when you stand
A steady reading below 90/60 with no symptoms is usually a healthy baseline. What matters is whether the pressure falls by 20/10 mmHg or more within 3 minutes of standing, and what the pulse does at the same time: a big pulse rise without a pressure fall suggests POTS, and a pressure fall with almost no pulse rise points to a nerve cause.
A reading of 88/58 in someone who feels well is usually that person's normal and needs nothing done. Low blood pressure starts to matter in three situations: it comes with dizziness or fainting, it falls when you stand up, or it is new and sudden. The causes are ranked below from most to least likely, with a way to check the standing drop on your own cuff and the blood tests that point to a cause.
What counts as low blood pressure
A blood pressure reading has two numbers. The top number (systolic) is the pressure while the heart beats; the bottom number (diastolic) is the pressure between beats. Both are given in mmHg (millimetres of mercury), the unit every cuff uses. The US National Heart, Lung, and Blood Institute (NHLBI) treats a reading below 90/60 mmHg as low, and notes that many people at that level have no symptoms and need no treatment 1. Younger adults, lean and physically fit people, and people in early pregnancy often run in that range 1. For the opposite direction, see high blood pressure.
Where an example systolic reading sitsmmHg (systolic)
Low readings are sorted by situation, not by grade, because the situation decides what happens next:
| Situation | Reading | What it usually means | Usual next step |
|---|---|---|---|
| Low, no symptoms | Below 90/60 mmHg at rest, steady over weeks | Your baseline; usually harmless 1 | Nothing beyond routine checks |
| Low with symptoms | Below 90/60 mmHg with dizziness, tiredness or blurred vision | Too little fluid or salt, a medicine, or an underlying cause 1 | Home stand test, medicine review, doctor visit |
| Drops on standing | Fall of 20 mmHg systolic or 10 mmHg diastolic within 3 minutes of standing 2 | Orthostatic hypotension | Doctor visit; blood tests for a cause |
| Sudden new drop | A new low reading with warning signs (see When it is urgent) | Shock from blood loss, infection, allergy or a heart cause 1 | Emergency: call 911 |
Low blood pressure symptoms
Symptoms come from the brain getting less blood for a few seconds or minutes. The telling pattern is symptoms that come on when you stand up or after standing still, and ease when you sit or lie down 1. If you feel well at a low reading, there is nothing to watch for.
- Lightheadedness or dizziness on standing
- Vision greying or tunnelling
- Tiredness and fatigue, poor concentration
- Nausea
- Feeling cold, with cold hands and feet
- A racing heart or palpitations on standing, the main symptom in POTS
- Fainting
When it is urgent
Is it really low?
A single low reading often reflects the conditions of the measurement more than the person. Check these before reading anything into one number:
- Timing after a meal: blood pressure can fall in the 1 to 2 hours after eating, mostly in older adults 7.
- Fluid loss: heat, hard exercise, vomiting, diarrhea or a day of fasting all lower blood pressure for a while 1.
- A blood pressure-lowering medicine taken an hour or two earlier (the full list is under causes) 4.
- The device: wrist and finger monitors are less reliable than a validated upper-arm cuff that fits your arm.
- Posture: a reading taken right after standing up measures a different thing from a seated reading after 5 minutes of rest.
To retest, take seated readings at the same times on several different days and write them down with any symptoms. The pattern counts for more than one number; see why a trend beats a single reading. If symptoms happen on standing, add the stand test below.
The lying-to-standing test at home
- 1Lie down for 5 minutesHave someone with you. Measure blood pressure and pulse while still lying flat. If you have had unexplained faints or falls, ask for this test in clinic instead.
- 2Stand up and measure at 1 minuteStand next to a chair or wall. Sit straight back down if you feel faint.
- 3Measure again at 3 minutesA fall of 20 mmHg systolic or 10 mmHg diastolic by 3 minutes meets the definition of orthostatic hypotension 2.
- 4Look at the pulseWhen nerve damage is the cause, the pulse barely rises while the pressure falls: a rise of less than about 0.5 beats per minute for each mmHg of systolic fall points that way 8. A pulse rise of 30 beats per minute or more (40 in ages 12 to 19) within 10 minutes, without a pressure drop, is the pattern of POTS (postural orthostatic tachycardia syndrome) 2.
- 5Write it all downRecord each reading, the pulse and how you felt, and take the log to your doctor.
Which kind of low blood pressure it is
Low blood pressure comes in several forms, and most have a defining number or trigger. Knowing the form narrows the causes.
| Type | When it happens | Defining number | Who tends to get it |
|---|---|---|---|
| Constitutional (your baseline) | All the time | Below 90/60 mmHg with no symptoms 1 | Younger, lean, fit people |
| Initial orthostatic hypotension | First 15 seconds of standing | Brief fall of more than 40 mmHg systolic or 20 mmHg diastolic 2 | Healthy young people; the common head rush |
| Orthostatic hypotension | Within 3 minutes of standing | Sustained fall of 20/10 mmHg or more 2 | Older adults, people on blood pressure drugs, diabetes, Parkinson's disease |
| POTS | Within 10 minutes of standing | Pulse rise of 30 beats per minute or more without a pressure drop 2 | Teens and younger adults |
| Postprandial hypotension | Within 2 hours of a meal | Systolic fall of 20 mmHg or more 7 | Older adults |
| Reflex (vasovagal) fainting | After a trigger: long standing, heat, pain, the sight of blood | Pressure and pulse drop together, then a faint | All ages; the most common cause of fainting 3 |
| Shock | Suddenly, with illness or injury | Low reading plus signs of poor circulation | Emergency at any age |
Read beside the stand test
What causes low blood pressure, from most to least likely
Doctors split low blood pressure into primary (constitutional: your body's normal setting) and secondary (caused by something else). Each secondary cause below has the clue that points to it and the test that checks it.
Common
- Your normal baseline. Clue: readings are always low and you feel fine. Check: repeat readings over several days; nothing else is needed 1.
- Too little fluid or salt, from heat, hard exercise, vomiting, diarrhea or fasting 1. Clue: thirst, dark urine, worse on hot days. Supporting clue: a raised BUN/creatinine ratio on a metabolic panel, which suggests dehydration but does not prove it.
- Medicines: diuretics, alpha-blockers (often for the prostate or blood pressure), nitrates (for chest pain), other blood pressure drugs, PDE5 inhibitors such as sildenafil (Viagra), tricyclic antidepressants and dopamine-based Parkinson's drugs. Clue: symptoms began after a new medicine or a dose change. Check: a medicine review with your doctor, which the 2017 consensus panel puts first 4.
- Reflex (vasovagal) fainting. Clue: a trigger, then warning signs such as sweating, nausea and tunnel vision. Check: the history, plus an ECG (heart tracing) to rule out a heart cause 3.
- Pregnancy. Clue: first or second trimester 9. Check: routine prenatal visits; fainting in pregnancy needs a same-day call to your care team.
Less common
- Anemia or slow blood loss: less oxygen-carrying blood. Clue: tiredness, breathlessness, pale skin. Check: hemoglobin and ferritin; see also iron deficiency.
- Nerve damage that blunts the standing reflex, from diabetes, Parkinson's disease or B12 deficiency. Clue: a big pressure fall with little pulse rise 48. Check: HbA1c (average blood sugar over about 3 months), vitamin B12, then specialist tests of the nerves that control blood pressure 4.
- Heart causes: a slow heart rate, valve disease or heart failure. Clue: breathlessness, or fainting on exertion or lying down. Check: ECG and echocardiogram (heart ultrasound) 3.
- Hormone causes: a severely underactive thyroid or episodes of low blood sugar. Clue: cold, slow and tired, or shaky and sweaty before meals. Check: TSH (thyroid-stimulating hormone) and glucose.
Must not miss
- Addison's disease (primary adrenal insufficiency). Clue: low blood pressure with salt craving, weight loss and darker skin; low sodium with high potassium. Check: a low morning cortisol with high ACTH (the pituitary hormone that tells the adrenals to make cortisol), then an ACTH stimulation test (an injection followed by cortisol checks over 30 to 60 minutes), where a peak cortisol below about 18 µg/dL (500 nmol/L) confirms it 5.
- Internal bleeding 1. Clue: black tarry stools, vomiting blood, very heavy periods. Test: hemoglobin, which can still be normal in the first hours of a bleed, so a normal result does not rule bleeding out.
- Sepsis 1. Clue: fever or feeling very cold, confusion, fast breathing. Tested in hospital.
- Anaphylaxis 1. Clue: swelling of the face or throat, hives, wheeze after a trigger. Use an epinephrine auto-injector right away if one has been prescribed, then call 911.
- Heart rhythm problems. Clue: palpitations right before fainting, or fainting during exercise. Check: ECG and heart monitoring 3.
Bleeding, sepsis, anaphylaxis and an adrenal crisis with a low reading are emergencies, and fainting with palpitations or during exercise needs same-day assessment; the signs are listed under When it is urgent.
Which blood tests find the cause of low blood pressure
No blood test measures blood pressure, but a standard blood panel finds most of the treatable causes. Most people with low blood pressure have normal results. Normal blood results do not rule out a heart cause or a recent bleed; the red flags above still apply.
| Test | Points to a cause when | Read more |
|---|---|---|
| Hemoglobin | Low: anemia or blood loss | Anemia |
| Ferritin | Low: iron deficiency behind the anemia | Iron deficiency |
| Vitamin B12 | Low: anemia plus possible nerve damage | B12 deficiency, vitamin deficiency symptoms |
| Sodium and potassium | Low sodium with high potassium: the Addison's pattern 5 | Low sodium, high potassium |
| Morning cortisol | Low, with the electrolyte pattern above: test for Addison's 5 | Low morning cortisol |
| BUN (blood urea nitrogen)/creatinine ratio | Raised: suggests dehydration; bleeding in the stomach or upper gut also raises it | High BUN/creatinine ratio |
| Fasting glucose and HbA1c | High: diabetes, a cause of nerve damage; low glucose: hypoglycemia | Diabetes, hypoglycemia |
| TSH | High: underactive thyroid | Hypothyroidism |
Markers that sort the causes
CalculatorBUN to creatinine ratio calculatorHave BUN and creatinine on your panel? Work out the ratio, a clue to dehydration.Work it out For how sodium, potassium and the kidney numbers fit together, see electrolytes explained. Not sure which of these your last panel included? See which blood tests to ask for.
What usually happens next
How a doctor usually works up low blood pressure
How to raise low blood pressure
These measures matter only when low blood pressure causes symptoms. A low number in someone who feels well needs no raising 1.
| Change | Effect measured in humans | Evidence | Source |
|---|---|---|---|
| Drinking about 500 mL of water quickly | Raised seated systolic pressure by roughly 30 mmHg or more in people with autonomic failure, within minutes and lasting about an hour; a smaller rise in healthy older adults | Human experimental study | 6 |
| Physical counter-pressure maneuvers (crossing legs and tensing, squatting, clenching buttocks) | Used at the first warning sign, reduced fainting episodes in a randomised trial | RCT, recommended by guideline | 3 |
| More fluid and salt | The ESC guideline describes 2 to 3 litres of fluid and about 10 g of salt a day for reflex fainting and orthostatic hypotension; targets are set with your doctor, and not for heart failure, kidney disease or high blood pressure | Guideline (expert consensus) | 3 |
| Compression stockings or an abdominal binder | Reduce blood pooling in the legs and belly on standing | Small RCTs, recommended by guideline | 34 |
| Raising the head of the bed by more than 10 degrees | Reduces night-time fluid loss and morning drops | Guideline (expert consensus) | 3 |
| Smaller meals with fewer refined carbs and less alcohol | Reduces after-meal drops | Consensus recommendation | 4 |
No supplement has good evidence for raising blood pressure. If the cause turns out to be anemia or B12 deficiency, treatment of that cause is guided by the blood results and your doctor.
Pregnancy and older adults
In pregnancy, blood pressure falls in the first and second trimesters and climbs back toward the usual level by term 9. Lying on the left side and standing in stages help many people; fainting in pregnancy is a reason to call the care team the same day. In older adults, drops on standing and after meals are more common and raise the risk of falls, so a medicine review and standing up in stages at night help most in this group 47.
Citations
- National Heart, Lung, and Blood Institute (NHLBI). Low Blood Pressure (hypotension): causes, symptoms, diagnosis and treatment. NIH, 2022.
- Freeman R, Wieling W, Axelrod FB, et al. Consensus statement on the definition of orthostatic hypotension, neurally mediated syncope and the postural tachycardia syndrome. Clin Auton Res. 2011;21(2):69-72.
- Brignole M, Moya A, de Lange FJ, et al. 2018 ESC Guidelines for the diagnosis and management of syncope. Eur Heart J. 2018;39(21):1883-1948.
- Gibbons CH, Schmidt P, Biaggioni I, et al. The recommendations of a consensus panel for the screening, diagnosis, and treatment of neurogenic orthostatic hypotension and associated supine hypertension. J Neurol. 2017;264(8):1567-1582.
- Bornstein SR, Allolio B, Arlt W, et al. Diagnosis and treatment of primary adrenal insufficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2016;101(2):364-389.
- Jordan J, Shannon JR, Black BK, et al. The pressor response to water drinking in humans: a sympathetic reflex? Circulation. 2000;101(5):504-509.
- Jansen RW, Lipsitz LA. Postprandial hypotension: epidemiology, pathophysiology, and clinical management. Ann Intern Med. 1995;122(4):286-295.
- Norcliffe-Kaufmann L, Kaufmann H, Palma JA, et al. Orthostatic heart rate changes in patients with autonomic failure caused by neurodegenerative synucleinopathies. Ann Neurol. 2018;83(3):522-531.
- Sanghavi M, Rutherford JD. Cardiovascular physiology of pregnancy. Circulation. 2014;130(12):1003-1008.
- Lewington S, Clarke R, Qizilbash N, Peto R, Collins R; Prospective Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet. 2002;360(9349):1903-1913.
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.
