Blood pressure is generally considered too low when it drops below 90/60 mmHg, but the number alone doesn’t tell the whole story. What matters more is whether that low reading causes symptoms. Some people walk around with a blood pressure of 85/55 their entire lives and feel perfectly fine. For others, a sudden drop from 110 to 90 systolic is enough to cause dizziness or fainting.
The Numbers That Matter
A blood pressure reading has two numbers. The top number (systolic) measures the force when your heart pumps. The bottom number (diastolic) measures pressure between beats. A reading below 90/60 mmHg is the standard threshold for low blood pressure, also called hypotension.
But here’s what catches people off guard: a sudden drop of just 20 mmHg in the top number can make you lightheaded or cause you to faint, even if your blood pressure doesn’t technically fall into the “low” range. Someone whose systolic pressure drops from 130 to 110 might feel just as woozy as someone sitting at 85. The speed and size of the change matter as much as the final number.
Severely low blood pressure, particularly readings well below 90/60, can reduce oxygen delivery to the brain and heart. That’s when low blood pressure shifts from a quirk of your physiology to a genuine medical concern.
Common Symptoms of Low Blood Pressure
If your blood pressure is too low, your brain isn’t getting enough blood flow. That’s why the most common symptoms are neurological: dizziness, lightheadedness, blurred or fading vision, and difficulty concentrating. Fatigue that doesn’t improve with rest is another hallmark. Some people also experience nausea or an upset stomach.
Fainting is the most dramatic symptom and also the most dangerous, not because of the blood pressure itself but because of what happens when you hit the ground. Falls from fainting cause head injuries, broken bones, and other trauma, especially in older adults. If you’re regularly feeling lightheaded when you stand up, that pattern is worth paying attention to even if your blood pressure looks acceptable on paper.
Orthostatic Hypotension: The Standing-Up Drop
One of the most common forms of low blood pressure happens when you go from sitting or lying down to standing. This is called orthostatic hypotension, and it’s diagnosed when your systolic pressure drops by 20 mmHg or your diastolic drops by 10 mmHg within two to five minutes of standing up. Gravity pulls blood toward your legs, and your body doesn’t compensate fast enough.
This type is especially common in older adults, people who are dehydrated, and those taking certain medications. It’s also the reason you might feel dizzy getting out of bed in the morning or standing up quickly from a chair. Rising slowly and pausing before walking gives your circulatory system time to adjust.
What Causes Chronically Low Blood Pressure
Some people simply have naturally low blood pressure as a baseline, and it never causes problems. Athletes and very fit individuals often have lower resting pressures because their cardiovascular system is efficient. This is not a concern.
When low blood pressure is new or getting worse, though, several underlying causes are worth considering. Dehydration is the most straightforward: less fluid in the bloodstream means less pressure pushing against artery walls. Nutritional deficiencies, particularly low levels of B12, folate, or iron, can reduce red blood cell production and lower blood pressure as a result. Endocrine problems like thyroid disorders or adrenal insufficiency can also be behind it, as can heart conditions that reduce the amount of blood your heart pumps with each beat.
Pregnancy is another common cause. Blood pressure typically falls during the first trimester and continues dropping into the second trimester. It usually returns to pre-pregnancy levels by the third trimester or shortly after delivery. This is a normal physiological shift, but it can cause dizziness and fatigue that many pregnant people don’t expect.
Medications That Lower Blood Pressure
If your blood pressure has dropped and you recently started or changed a medication, that’s often the culprit. The most obvious offenders are drugs prescribed specifically to lower blood pressure, including diuretics (water pills) that reduce fluid volume. But several other medication classes can cause blood pressure drops as a side effect.
Tricyclic antidepressants, certain antipsychotic medications, drugs used to treat Parkinson’s disease, and nitrate medications for chest pain can all cause orthostatic hypotension. If you take a nitrate alongside medication for erectile dysfunction, the blood pressure drop can be particularly steep. Even some over-the-counter antihistamines can contribute. If you suspect a medication is behind your symptoms, that’s a conversation to have with whoever prescribed it, since adjusting the dose or timing can often solve the problem.
Low Blood Pressure After Eating
Older adults sometimes experience a noticeable blood pressure drop within two hours of eating a meal. This is called postprandial hypotension, defined as a systolic drop of 20 mmHg or more after eating. It happens because digesting food diverts a large volume of blood to the abdomen, and the body’s automatic compensation mechanisms don’t respond strongly enough to maintain pressure elsewhere.
Carbohydrate-heavy meals, particularly those high in sugar, tend to cause the biggest drops. Eating smaller, more frequent meals with lower carbohydrate content can reduce the effect. Some research has also looked at drinking water before eating as a way to buffer the drop, though the evidence is still being sorted out.
When Low Blood Pressure Is an Emergency
Low blood pressure becomes dangerous when it progresses to shock, a condition where organs aren’t receiving enough blood to function. The signs go well beyond mild dizziness. Skin becomes pale, cool, and clammy. Breathing turns rapid and shallow. The pulse feels weak and fast, or it may be hard to detect at all. Confusion, excessive sweating, and loss of consciousness are all warning signs.
Shock can result from severe blood loss, serious infections, severe allergic reactions, or major heart problems. It requires emergency medical treatment. If someone around you shows these symptoms, calling emergency services immediately is critical.
Lifestyle Strategies for Managing Low Blood Pressure
For people with chronically low blood pressure that causes symptoms, increasing salt and fluid intake is one of the first-line strategies. This is the opposite of the advice given to most Americans, who are told to cut sodium. For people with orthostatic hypotension, medical guidelines recommend between 2,400 and 4,000 mg of sodium per day, and some specialists push that even higher depending on the severity. For context, the average dietary guideline for the general population caps sodium at 2,300 mg.
Beyond sodium, several practical habits help. Standing up slowly from sitting or lying positions gives your body time to adjust. Compression stockings prevent blood from pooling in your legs. Avoiding alcohol helps, since it dilates blood vessels and lowers pressure further. Eating smaller, more frequent meals reduces the postprandial dip. Staying well hydrated throughout the day, rather than drinking large amounts at once, keeps blood volume steadier.
If these strategies aren’t enough and symptoms interfere with daily life, prescription options exist. But for most people, the combination of salt, fluids, and movement habits makes a significant difference.