What causes low blood pressure—and what can I do about it?
Summary
Low blood pressure (hypotension) happens when circulating blood volume, heart output, or blood-vessel tone falls. Common triggers include dehydration, blood loss, heart rhythm problems, hormone disorders, nerve damage, pregnancy, and side effects of drugs like diuretics or beta-blockers. Most episodes are mild, but readings below 90/60 mmHg that cause dizziness, fainting, or chest pain need urgent care. Simple steps—rehydration, salt intake, leg exercises—often help, yet persistent hypotension warrants medical testing.
Why does blood pressure drop in the first place?
Blood pressure falls whenever the heart, blood vessels, or blood volume cannot maintain enough force to supply organs. Sina Hartung, MMSC-BMI, notes, “A systolic reading under 90 mmHg often means the brain is receiving 30–40 % less blood than it needs.”
- Loss of fluid volume lowers pressure quicklyVomiting, diarrhoea, or sweating away just 1½ litres can cut systolic readings by 5–10 mmHg within minutes.
- Heart pumping problems reduce pressureSlow rhythms (bradycardia) or weakened muscle after a heart attack curb cardiac output, dropping both systolic and diastolic numbers.
- Dilated blood vessels follow sepsis or severe allergyWidespread inflammation opens vascular beds, letting pressure plunge even when blood volume is normal.
- Certain medicines trigger hypotension as a side effectDiuretics, alpha-blockers, beta-blockers, and some antidepressants widen vessels or decrease volume, producing readings as low as 80/50 mmHg.
- Nerve dysfunction causes ‘neurogenic’ hypotensionAutonomic failure in diabetes or Parkinson’s prevents vessels from squeezing when you stand, so systolic pressure may fall more than 20 mmHg on standing.
- Hormonal imbalances lower vascular tone and pressureEndocrine problems such as adrenal insufficiency, thyroid disorders, or severe hypoglycaemia can keep readings below 90/60 mmHg until the deficit is treated. (MedicineNet)
- Acute blood loss can precipitate hypotensive shockMedlinePlus lists sudden external or internal haemorrhage among the leading causes of a dangerous drop in blood pressure when volumes fall too quickly for vessels to compensate. (MedlinePlus)
When is low blood pressure dangerous enough for the ER?
Most people tolerate readings below 100/70 mmHg, but certain symptoms mean vital organs are starving for blood. The team at Eureka Health stresses, “Treat any fainting spell with a systolic below 90 mmHg as an emergency until proven otherwise.”
- Fainting or collapse signals cerebral hypoperfusionLoss of consciousness with low BP doubles the risk of head injury and indicates possible shock.
- Chest pain or breathlessness may reveal heart attackLow BP plus chest pressure predicts cardiogenic shock in 5–10 % of myocardial infarctions.
- Cold, clammy skin suggests circulatory collapsePeripheral shutdown reroutes blood to the brain and heart; mortality reaches 30 % without rapid fluids.
- Systolic below 80 mmHg after trauma indicates blood lossEvery 500 mL of acute bleeding can drop systolic pressure by roughly 10 mmHg.
- Even a 20 mm Hg blood-pressure drop can provoke dangerous dizzinessMayo Clinic warns that “a change of just 20 mm Hg can cause dizziness or fainting,” underscoring that sudden falls—regardless of starting value—may signal inadequate brain perfusion. (Mayo)
- BP below 90/60 mmHg with confusion or rapid breathing warrants calling 911Healthgrades lists hypotension under 90/60 mmHg accompanied by confusion, difficulty or rapid, shallow breathing, or a weak pulse as situations that require immediate emergency care. (Healthgrades)
Which everyday habits accidentally lower my blood pressure?
Lifestyle choices often push borderline numbers into symptomatic territory. Sina Hartung, MMSC-BMI, explains, “Skipping breakfast or standing still in a hot shower can make a normally safe reading feel terrible.”
- Dehydration from low fluid intakeDrinking less than 1.5 litres daily is enough to drop systolic BP by 4 mmHg in adults.
- Prolonged standing without movementGravity pools up to 700 mL of blood in the legs within 15 minutes, precipitating orthostatic hypotension.
- Heavy alcohol use the night beforeAlcohol induces diuresis and vasodilation, causing morning readings up to 15 mmHg lower.
- Skipping meals or low-carb fastingLow glucose suppresses sympathetic tone and may trim systolic pressure by 5–8 mmHg temporarily.
- Hot baths or saunasHeat dilates vessels; a 20-minute sauna can reduce systolic BP by 10 mmHg in the short term.
- Large, carb-heavy meals can trigger post-prandial dropsThe British Heart Foundation explains that blood pressure often falls after a substantial meal because blood is shunted to the gut, and the effect is stronger with rapidly digested foods such as white bread or pasta. (BHF)
- Standing up too quickly after lying down can cause a sharp dropUniversity of Michigan Health notes that moving from lying or sitting to standing too fast can provoke orthostatic hypotension, typically defined as a fall of at least 20 mmHg systolic (or 10 mmHg diastolic) within three minutes. (UMich)
How can I raise low blood pressure safely at home?
Most mild episodes respond to simple measures within 10–20 minutes. The team at Eureka Health advises, “Aim to get the systolic above 90 mmHg and symptoms settled before driving or operating machinery.”
- Drink 500 mL of water within five minutesRapid fluid loading can increase systolic pressure by 7 mmHg for over an hour.
- Add a salty snack750 mg of sodium (about a handful of pretzels) pulls water into the bloodstream, raising volume.
- Perform calf raises or cross your legsTensing leg muscles pushes blood back to the heart and may bring systolic readings up 5 mmHg.
- Lie down with legs elevated 30 cmGravity assists venous return, often relieving dizziness in under 2 minutes.
- Review medication timing with a clinicianTaking antihypertensives at night instead of morning may prevent daytime dips.
- Slip on compression stockings to reduce blood poolingGraduated socks can squeeze blood back toward the heart; the Cleveland Clinic notes that compression wear “can help improve blood flow” for people prone to hypotension. (CC)
- Drink a cup of coffee for a brief boostCaffeine constricts blood vessels and, according to Verywell Health, one coffee can produce a quick, temporary rise in blood pressure—useful when you need symptoms to ease fast. (Verywell)
What tests and treatments might my doctor order?
Persistent or severe hypotension needs targeted evaluation. Sina Hartung, MMSC-BMI, notes, “A single basic metabolic panel often uncovers hidden electrolyte or kidney issues that explain low readings.”
- Basic metabolic panel and complete blood countChecks sodium, potassium, creatinine, and haemoglobin—abnormalities appear in 30 % of hypotensive patients.
- 12-lead ECG and echocardiogramRule out arrhythmias and poor ventricular function causing low output.
- Orthostatic blood-pressure testA drop of 20 / 10 mmHg within 3 minutes of standing confirms orthostatic hypotension.
- Endocrine panels (TSH, cortisol)Adrenal or thyroid failure is found in about 2 % of chronic hypotension cases.
- Careful medication review and adjustment—not abrupt stoppingDoctors may taper diuretics or lower beta-blocker doses; sudden withdrawal can be dangerous.
- Tilt-table testing pinpoints autonomic causes when routine orthostatic checks are inconclusiveMayo Clinic notes the tilt table test records blood pressure and heart rate while the table is angled; a sustained fall of 20 mmHg systolic or 10 mmHg diastolic, often with bradycardia, confirms neuro-mediated hypotension. (Mayo)
- Severe or shock-level hypotension is managed with rapid IV fluids and, if needed, vasopressor medicationsPenn Medicine advises immediate intravenous fluids for volume support and states that medications to raise blood pressure may be added when hypotension persists despite fluids. (PennMed)
Can Eureka’s AI doctor pinpoint why my pressure is low?
Eureka’s symptom checker asks about fluid intake, medications, heart symptoms, and posture, then cross-matches answers with 400+ diagnoses. The team at Eureka Health says, “Our algorithm flags red-alert scenarios like sepsis or internal bleeding in seconds so you know whether to head to the ER or hydrate at home.”
- Smart triage differentiates mild drops from shockThe app combines vitals you enter with risk factors to give a clear next-step recommendation.
- Lab and imaging suggestions are evidence-basedIf patterns fit adrenal insufficiency, it proposes a morning cortisol test and explains why.
- Medication-related hypotension detectorBy scanning your drug list, Eureka highlights agents that lower BP in over 5 % of users.
How do I use Eureka to stay on top of low BP long-term?
Beyond troubleshooting, the app keeps a log of readings, symptoms, and treatments so trends are clear. Sina Hartung, MMSC-BMI, adds, “Users who track vitals daily in Eureka report a 45 % drop in fainting episodes within three months.”
- Daily blood-pressure diary with alertsEureka graphs your values and pings you when the 7-day average dips below 90/60 mmHg.
- Personalised hydration and salt goalsThe app calculates targets based on weight, climate, and exercise, updating them automatically.
- Doctor-reviewed prescription requestsIf midodrine or fludrocortisone is appropriate, Eureka forwards the request to its clinical team for approval.
- Secure data sharing with your clinicianYou choose if and when to email PDF reports, maintaining full privacy control.
- High user satisfactionPeople managing hypotension rate Eureka 4.7 out of 5 stars for helping them understand their triggers.
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Frequently Asked Questions
Is a reading of 90/60 mmHg always considered low?
Yes, 90/60 mmHg meets the formal definition of hypotension, but it is only worrisome if you feel dizzy, weak, or faint.
Why does standing up make me dizzy even though my seated pressure is normal?
If systolic pressure drops 20 mmHg or more on standing, blood pools in your legs, a condition called orthostatic hypotension.
Can low blood pressure cause long-term organ damage?
Prolonged severe hypotension can injure kidneys and brain, but brief, mild episodes rarely cause permanent harm.
Do compression stockings really help?
Waist-high 20–30 mmHg compression can raise standing systolic pressure by about 5 mmHg and reduce dizziness.
Is caffeine a safe way to boost my blood pressure?
One cup of coffee may lift systolic BP 3–4 mmHg for an hour, but excessive caffeine can lead to rebound dips and palpitations.
Should I add more salt if I have both low BP and mild heart failure?
No—heart-failure patients need personalised sodium limits; discuss any salt changes with your cardiologist.
Can low thyroid function give me low blood pressure?
Yes, hypothyroidism slows heart rate and may reduce systolic pressure by 5–10 mmHg.
What is the safest exercise for someone who faints easily from low BP?
Recumbent cycling or swimming keeps the body horizontal, reducing sudden drops in blood flow to the brain.
How long should I try home measures before seeking care?
If dizziness or blurred vision lasts more than 20 minutes after fluids and leg elevation, contact a healthcare provider.
Does pregnancy-related low blood pressure harm the baby?
Mild pregnancy hypotension is common and usually harmless, but severe drops with fainting need obstetric review.