Low blood pressure, called hypotension, is any reading below 90/60 mmHg. That means either your top number (systolic) is under 90, your bottom number (diastolic) is under 60, or both. For many people, readings in this range cause no problems at all. The number only becomes a concern when it triggers symptoms or drops suddenly.
What the Numbers Mean
A blood pressure reading has two numbers. The top number (systolic) measures the force of blood against artery walls when your heart beats. The bottom number (diastolic) measures that force between beats, when your heart is resting. A normal reading falls below 120/80 mmHg. Once either number dips below the 90/60 threshold, it’s classified as low.
But context matters more than the number itself. Someone who consistently reads 85/55 and feels fine has no medical problem. Someone whose pressure suddenly falls from 110 to 90 systolic can feel dizzy, lightheaded, or faint, even though 90 is only slightly below the cutoff. A sudden change of just 20 mmHg in the top number is enough to cause symptoms, regardless of where you started.
When Low Blood Pressure Causes Symptoms
Many people with blood pressure below 90/60 never notice a thing. When symptoms do appear, they typically include lightheadedness, feeling faint, blurred vision, nausea, fatigue, or trouble concentrating. You might feel sluggish or unusually tired without an obvious reason. Some people notice pale skin, rapid shallow breathing, or a weak, fast pulse.
These symptoms tend to show up when you stand quickly, haven’t eaten in a while, or are dehydrated. If low blood pressure reaches extreme levels, it can reduce blood flow to your organs. In severe cases, this leads to shock, where organs start shutting down from lack of oxygen. Signs of shock include confusion (especially in older adults), cold and clammy skin, and rapid breathing. This is a medical emergency.
Types of Low Blood Pressure
Orthostatic Hypotension
This is the most commonly diagnosed form. It’s defined as a drop of 20 mmHg or more in systolic pressure, or 10 mmHg or more in diastolic pressure, within three minutes of standing up from a lying position. If you already have high blood pressure while lying down, the threshold is higher: a 30 mmHg systolic drop. This type is especially common in older adults and can happen without any noticeable symptoms. Even when you don’t feel dizzy, asymptomatic drops of this size are linked to higher cardiovascular risk over time. One study of home-dwelling older adults found that diastolic drops of 8 mmHg or more on standing were associated with increased risk of heart attack.
Postprandial Hypotension
Some people experience a blood pressure drop after eating. The top number typically falls about 20 mmHg within 30 to 60 minutes of a meal. Blood flows to the digestive system to help process food, and in some people, the body doesn’t compensate quickly enough to keep pressure stable. This is more common in older adults, particularly those who already have high blood pressure or a nervous system condition like Parkinson’s disease.
Neurally Mediated Hypotension
This happens when the communication between your heart and brain misfires, usually after standing for a long period. Your body incorrectly signals the heart to slow down instead of speeding up, causing pressure to plummet. During medical testing, doctors tilt patients upright on a table and monitor for a systolic drop to around 70 mmHg or the appearance of symptoms like faintness. This type is more common in younger adults and children.
Common Causes
Dehydration is one of the most frequent triggers. When your body loses more fluid than it takes in, blood volume drops and pressure follows. This can happen from heat exposure, vomiting, diarrhea, or simply not drinking enough water. Blood loss from an injury or surgery has the same effect but more dramatically.
Medications are a major contributor, especially in older adults. Blood pressure drugs, including ACE inhibitors, calcium-channel blockers, and beta-blockers, can sometimes push pressure lower than intended. Antidepressants (particularly SSRIs) and medications used for prostate issues (alpha-blockers) also commonly cause drops in blood pressure, especially on standing. The risk increases when several of these medications are taken together.
Heart conditions like very slow heart rate, heart valve problems, and heart failure can all reduce the amount of blood your heart pumps out. Hormone problems, including thyroid disorders and adrenal insufficiency, affect how your body regulates fluid balance and vessel tone. Severe infections and serious allergic reactions can cause a sudden, dangerous drop in blood pressure as blood vessels widen rapidly.
Pregnancy commonly lowers blood pressure, particularly during the first 24 weeks, as the circulatory system expands to support the developing baby. This usually resolves after delivery.
Do Athletes Have Naturally Low Readings?
You might expect highly trained athletes to have significantly lower blood pressure, but the difference is smaller than most people assume. A study of nearly 3,700 young athletes found their blood pressure was only about 3 to 4 mmHg lower than non-athletes of the same age. Male athletes averaged around 126/80, and female athletes averaged about 116/75. Endurance and speed athletes tended to have slightly lower readings than power athletes. So while regular exercise does help keep blood pressure in a healthy range, it doesn’t typically push it into territory that would be classified as hypotension.
What Matters More Than a Single Number
A single low reading on its own is rarely cause for concern. What matters is the pattern: how your pressure changes when you stand, eat, or take medications, and whether those changes cause symptoms. If you consistently read below 90/60 and feel perfectly well, that’s your normal baseline. Some people run low their entire lives without any health consequences.
The picture changes for older adults. Even blood pressure drops that don’t cause noticeable symptoms can carry risk. Larger drops in both the top and bottom numbers on standing have been linked to higher rates of cardiovascular events and mortality in older populations. This is why doctors often check blood pressure in both lying and standing positions during routine visits, especially for people over 65 or those taking multiple medications.
If you notice frequent dizziness when standing, persistent fatigue, or episodes of near-fainting, tracking your blood pressure at home can help identify whether low readings are the cause. Note the time of day, whether you’ve just eaten, and what position you were in. That information is far more useful than any single number on its own.