When it comes to blood pressure, lower is generally better. Like a gushing stream that erodes its banks, high blood pressure can damage blood vessels over time. And this can lead to a slew of health-harming issues, including heart disease, vision loss and kidney failure.
But it turns out that going too low can be too much of a good thing.
Low blood pressure is called hypotension. It’s rarely treated with medication, says Jennifer Wong, MD. She’s a cardiologist and medical director of non-invasive cardiology at Orange Coast Medical Center in Fountain Valley, California.
Still, low blood pressure is enough of a concern to keep an eye on. That’s because when blood pressure dips, it can lead to unpleasant symptoms. And some are more dangerous than others.
Here’s what worries experts about low blood pressure, and what you can do to stay safe.
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When is blood pressure considered too low?
First, let’s go over how blood pressure is measured. Doctors use 2 numbers to assess your blood pressure:
Systolic blood pressure (the first number) tells you how much pressure your blood exerts against your artery walls when your heart beats.
Diastolic blood pressure (the second) tells you how much pressure your blood exerts against your artery walls when your heart is resting between beats.
According to the American Heart Association (AHA), normal blood pressure is less than 120 mm Hg systolic and less than 80 mm Hg diastolic. In general, a blood pressure reading below 90/60 mm Hg is considered low. But doctors typically rely on your symptoms to tell you whether it’s a problem.
(For more on high blood pressure — and how to keep it in check — click here.)
What are the signs of low blood pressure?
Most doctors won’t consider low blood pressure an issue unless it affects your quality of life.
There are 3 major signs that can point to low blood pressure. They are:
- Dizziness or lightheadedness, especially when standing up suddenly or standing in place for a long time. This is called orthostatic hypotension. It happens when your blood pressure drops quickly due to a change in physical position, especially standing. You’ll feel a “head rush” moment of dizziness, which may throw you off balance. Dr. Wong says this can be worse with issues such as dehydration or acute illness.
- Brain fog or lack of concentration. Lower blood pressure could mean less blood is getting to your brain. This may make it harder to multitask or focus. Or it could bring on mild memory problems.
- Low energy, even when you’ve had enough sleep. You got your 8 hours — but you’re still dragging. When your organs and muscles don’t get enough blood, this can cause fatigue. Some experts at the Centers for Disease Control and Prevention (CDC) have suggested that chronic fatigue syndrome and low blood pressure may be linked.
Less common symptoms include nausea, headache, blurred vision, shallow breathing, mood changes, rapid heart rate, excess sweating and cold skin.
Dr. Wong says you should check with your doctor if these symptoms become an issue or limit your everyday activities. If you experience fainting, sudden weakness or shortness of breath, you should go to the emergency room.
What causes low blood pressure?
There are many possible factors, but a top cause is dehydration, says Seema Bonney, MD. She’s the founder and medical director of the Anti-Aging and Longevity Center of Philadelphia.
Almost half of your blood volume is water. It helps shuttle blood cells, nutrients and all the other good stuff that keeps you going to the places they need to be. When you’re low on water, that can mean less blood volume and, in turn, less pressure against your blood vessels.
According to the AHA, other possible causes of low blood pressure include:
- Pregnancy. During pregnancy, the body secretes a hormone called progesterone, explains Dr. Bonney. Progesterone helps to relax blood vessel walls and increases the flow of blood to the mother and the baby. And this lowers blood pressure.
- Hormone-related disorders. An example is an underactive thyroid (called hypothyroidism). When you don’t have enough thyroid hormone, your heart rate can slow. And this can lower blood pressure.
- Certain medications. High blood pressure medications can sometimes work too well. (That’s why it’s important to revisit your medications and doses with your doctor at each visit.) Tricyclic antidepressants and erectile dysfunction medications can also lower your blood pressure.
- Heart problems. Issues such as heart failure can make it hard for the heart to pump enough blood to meet your body’s needs. And this can put your organs and other body systems at risk.
