Low blood pressure, called hypotension, is generally defined as a reading below 90/60 mmHg. That means a systolic pressure (top number) under 90 or a diastolic pressure (bottom number) under 60. Unlike high blood pressure, which has strict categories in clinical guidelines, low blood pressure doesn’t have a single official cutoff in the 2025 AHA/ACC blood pressure guidelines. What matters most is whether your numbers are causing symptoms and how far they’ve dropped from your personal baseline.
How Blood Pressure Numbers Work
A blood pressure reading has two numbers. The top number (systolic) measures the force when your heart pumps blood out. The bottom number (diastolic) measures the pressure between beats, when the heart is refilling. Normal blood pressure is defined as below 120/80 mmHg in the 2025 guidelines. The space between “normal” and “low” is a gray zone that depends heavily on the individual.
Someone who normally runs 115/75 and drops to 90/55 may feel terrible, while someone who has always lived at 95/62 might feel perfectly fine. A drop from 110 systolic to 90 systolic, for instance, can be enough to trigger noticeable symptoms even though 90 isn’t dramatically low on paper. That’s why clinicians focus less on a single threshold and more on the size and speed of the drop.
When Low Blood Pressure Causes Symptoms
Many people walk around with blood pressure in the low-normal range and never notice. Low blood pressure only becomes a medical concern when it reduces blood flow enough to produce symptoms. The most common signs include:
- Lightheadedness or dizziness, especially when standing up
- Blurred vision
- Nausea
- Fatigue or feeling unusually weak
- Fainting
These symptoms tend to appear when blood pressure drops quickly rather than sitting at a consistently low level. Your brain is especially sensitive to changes in blood flow, so even a modest dip can leave you feeling off-balance if it happens fast.
Types of Low Blood Pressure
Orthostatic Hypotension
This is the most commonly diagnosed form. It happens when your blood pressure drops after you stand up from sitting or lying down. The formal criteria are a drop of 20 mmHg or more in systolic pressure, or 10 mmHg or more in diastolic pressure, within two to five minutes of standing. You’ve probably felt a milder version of this if you’ve ever stood up too fast and gotten a brief head rush. When it happens frequently or causes fainting, it warrants medical attention.
Postprandial Hypotension
Blood pressure can drop after eating, particularly large meals. This form is defined by a systolic drop of about 20 mmHg after a meal and is more common in older adults. Digestion diverts blood toward the gut, and in some people the body doesn’t compensate quickly enough. Eating smaller, more frequent meals and limiting refined carbohydrates can help reduce these episodes.
Neurally Mediated Hypotension
This type causes blood pressure to drop after standing for long periods. It’s especially common in younger people and children. The brain and heart miscommunicate, triggering a drop in pressure and heart rate at the same time. Fainting in hot, crowded environments or during prolonged standing is a classic pattern.
Who Naturally Runs Low
Some people have blood pressure that sits below 90/60 as their normal baseline, and this is not inherently dangerous. Endurance athletes often develop lower resting blood pressure because their hearts are more efficient at pumping blood per beat. Younger adults, particularly women, tend to have lower readings as well.
During pregnancy, blood pressure commonly drops during the first and second trimesters as the circulatory system expands rapidly to support the growing fetus. This is expected and usually resolves in the third trimester. Pregnant individuals are typically monitored for high blood pressure (above 140/90) rather than low, since pre-eclampsia poses a greater risk. Still, if low readings are causing persistent dizziness or fainting during pregnancy, it’s worth mentioning to your provider.
Common Causes of Low Readings
Dehydration is one of the most frequent and easily reversible causes. When your blood volume drops, even modestly, pressure falls with it. This is why blood pressure can dip after vigorous exercise, prolonged heat exposure, vomiting, or diarrhea.
Medications are another major contributor. Blood pressure drugs, diuretics (water pills), certain antidepressants, and medications for Parkinson’s disease can all lower blood pressure further than intended. This is particularly common when doses change or when multiple medications interact. Heart conditions that slow the heart rate, hormonal problems like adrenal insufficiency, and significant blood loss from injury or surgery can also push pressure into a low range.
Nutritional deficiencies play a role too. Low levels of vitamin B12, folate, or iron can reduce the body’s ability to produce enough red blood cells, leading to anemia and lower blood pressure as a downstream effect.
When Low Blood Pressure Becomes Dangerous
Systolic pressure below 90 mmHg is the clinical threshold used in intensive care settings to define hypotension that requires intervention. When blood pressure drops this low and organs aren’t receiving enough blood, the condition progresses toward shock. Signs of shock go beyond simple dizziness and include confusion (especially in older adults), cold and clammy skin, skin that looks noticeably pale, rapid and shallow breathing, and a weak, fast pulse.
Shock is most often triggered by severe bleeding, serious infections (sepsis), or severe allergic reactions (anaphylaxis). These are emergencies where the blood pressure drop is sudden and extreme. The danger isn’t the number on the monitor alone but the fact that vital organs, particularly the brain, kidneys, and heart, are being starved of oxygen.
What to Do About Consistently Low Readings
If your blood pressure is consistently below 90/60 but you feel fine, there’s generally nothing to treat. Low blood pressure without symptoms is not a disease.
If you’re getting symptoms, a few practical strategies can help. Increasing fluid intake, especially water and drinks with electrolytes, supports blood volume. Adding a bit more salt to your diet (the opposite of what people with high blood pressure are told) can help raise pressure slightly. Wearing compression stockings can reduce blood pooling in the legs, which is particularly useful for orthostatic hypotension. Standing up slowly, avoiding prolonged standing, and eating smaller meals can all reduce the frequency of symptomatic drops.
Keeping a log of your blood pressure readings at different times of day, along with any symptoms, gives a much clearer picture than a single reading at a doctor’s visit. Home monitors are inexpensive and widely available. What you’re looking for isn’t just the number, but the pattern: does your pressure drop after meals, upon standing, in the morning, or seemingly at random? That pattern points toward the type of hypotension and the most effective way to manage it.