Hypotension, or low blood pressure, is generally defined as a reading below 90/60 mmHg. That means either a systolic pressure (the top number) under 90 or a diastolic pressure (the bottom number) under 60. But the number alone doesn’t always tell the full story. Some people walk around with naturally low blood pressure and feel perfectly fine, while others experience symptoms at readings that technically fall within a normal range.
The Numbers That Define Hypotension
Normal blood pressure falls between 90/60 and 120/80 mmHg. The 2025 guidelines from the American Heart Association and American College of Cardiology classify blood pressure into four categories: normal (below 120/80), elevated (120-129 systolic with diastolic still under 80), stage 1 hypertension (130-139 systolic or 80-89 diastolic), and stage 2 hypertension (140+ systolic or 90+ diastolic). Hypotension sits at the opposite end of that spectrum, below 90/60.
Clinicians sometimes use a different metric called mean arterial pressure (MAP), which reflects the average pressure in your arteries during a full heartbeat cycle. A MAP below 65 mmHg is another way hypotension can be defined, and it’s particularly relevant in hospital settings where continuous monitoring is available.
The important distinction is between low blood pressure as a number and low blood pressure as a problem. If your readings consistently land around 85/55 but you feel energetic and alert, that’s your baseline, not a condition that needs treatment. Hypotension becomes clinically significant when the low pressure causes symptoms or signals an underlying issue.
Symptoms That Signal a Problem
The hallmark symptom of hypotension is lightheadedness or dizziness, especially when standing up. This happens because your brain temporarily isn’t getting enough blood flow. Other common signs include blurry vision, nausea, fatigue, and difficulty concentrating. In more pronounced cases, you might feel unsteady on your feet or actually faint.
Cold, clammy skin and a pale complexion can accompany a significant drop in blood pressure. Some people describe a general sense of weakness or feeling “off” without being able to pinpoint exactly what’s wrong. If these symptoms appear regularly, particularly in connection with position changes, meals, or certain medications, that pattern itself is diagnostically useful.
Types of Hypotension
Orthostatic Hypotension
Orthostatic hypotension is the type most people have experienced at least once: you stand up too quickly and the room briefly spins. It’s formally defined as a drop of at least 20 mmHg in systolic pressure or 10 mmHg in diastolic pressure within three minutes of standing after lying down for at least five minutes. Your cardiovascular system normally compensates for gravity’s effect on blood flow within seconds, but when that reflex is sluggish or impaired, blood pools in your legs and your brain gets shortchanged.
Dehydration, prolonged bed rest, and aging all make orthostatic hypotension more likely. It’s also a common side effect of blood pressure medications, antidepressants, and drugs used for prostate conditions. In older adults, it’s a significant risk factor for falls.
Postprandial Hypotension
Blood pressure can also drop after eating, a phenomenon called postprandial hypotension. It’s defined as a fall of at least 20 mmHg in systolic pressure within two hours after a meal. Digestion redirects a substantial volume of blood to your gut, and in some people, the body doesn’t compensate well enough to maintain pressure elsewhere. This type disproportionately affects older adults and is sometimes described as a “silent” contributor to falls and fainting in that population. Large, carbohydrate-heavy meals tend to trigger the biggest drops.
Neurally Mediated Hypotension
Some people experience sudden drops in blood pressure after standing for long periods, exposure to heat, or emotional stress. This happens when the communication between the heart and brain misfires: instead of raising blood pressure to compensate, the nervous system sends a signal that lowers it. The result is often fainting. This type is particularly common in younger adults and teenagers.
What Causes Chronic Low Blood Pressure
Beyond the situational types, several underlying conditions can keep blood pressure persistently low. Heart problems like very slow heart rate, heart valve disease, or heart failure reduce the volume of blood the heart pumps with each beat. Endocrine disorders affecting the thyroid or adrenal glands can disrupt hormones that help regulate pressure. Significant blood loss from an injury or internal bleeding drops blood volume directly. Severe infections can cause blood vessels to dilate dramatically, pulling pressure down.
Dehydration is one of the most common and most fixable causes. When your body loses more water than it takes in, even mild dehydration reduces blood volume enough to lower pressure and trigger dizziness or fatigue. Nutritional deficiencies in vitamin B12, folate, or iron can lead to anemia, which in turn can cause low blood pressure because the blood isn’t carrying oxygen efficiently.
Medications deserve special attention. Diuretics (water pills), beta-blockers, calcium channel blockers, and drugs for Parkinson’s disease or depression can all lower blood pressure as a primary or side effect. If you notice symptoms after starting a new medication, that timing is worth noting.
When Low Blood Pressure Becomes Dangerous
At its most severe, hypotension becomes shock, a life-threatening emergency where organs aren’t getting enough oxygen to function. Shock is most commonly identified by a systolic pressure below 90 mmHg or a MAP below 65, combined with signs like rapid heart rate, rapid breathing, confusion or altered mental state, cold and mottled skin, and very low urine output.
Shock can result from massive blood loss, severe infection (sepsis), a serious allergic reaction (anaphylaxis), or heart failure. It progresses quickly: cells starved of oxygen begin to die, and organ damage can become irreversible. This isn’t the kind of low blood pressure you manage at home. A person showing signs of shock needs emergency care immediately.
How Hypotension Is Diagnosed
A standard blood pressure reading is the starting point, but a single low reading doesn’t necessarily mean you have hypotension. Your doctor will likely want multiple readings taken at different times and in different positions (lying down, sitting, standing) to see how your pressure responds to changes.
For orthostatic hypotension specifically, the test is straightforward: your pressure is measured after lying down for five minutes, then again after standing. If the drop meets the 20/10 mmHg threshold within three minutes, the diagnosis is confirmed.
When fainting is involved and the cause isn’t clear, a tilt table test can help. You lie on a table that’s gradually tilted to an upright position while your blood pressure and heart rhythm are monitored continuously. The passive phase of this test lasts 20 to 45 minutes, and sometimes a medication is given to increase the test’s sensitivity. The goal is to reproduce the conditions that trigger your symptoms in a controlled environment, helping distinguish between neurally mediated fainting, orthostatic hypotension, and other causes. Blood tests to check for anemia, blood sugar problems, or thyroid dysfunction are often part of the workup as well.
Managing Low Blood Pressure
For many people, simple lifestyle adjustments are enough. Drinking more water throughout the day increases blood volume. Adding a bit more salt to your diet (the opposite of the advice given for high blood pressure) can help your body retain fluid. Wearing compression stockings prevents blood from pooling in your legs.
If orthostatic hypotension is the issue, getting up slowly, in stages, makes a real difference. Sit on the edge of the bed for a minute before standing. Avoid standing motionless for long periods. For postprandial hypotension, eating smaller, more frequent meals and limiting refined carbohydrates can blunt the post-meal drop.
When a medication is the culprit, adjusting the dose or switching to an alternative often resolves the problem. If an underlying condition like a thyroid disorder or anemia is driving the low pressure, treating that condition brings blood pressure back up as a result. In cases where lifestyle changes aren’t enough, prescription options exist that work by either constricting blood vessels or increasing blood volume, but the specifics depend on the type and cause of hypotension involved.