What is blood pressure?

Blood pressure is the force that’s exerted by your blood on the walls of your arteries. Arteries are a type of blood vessel that carry oxygen-rich blood away from your heart, delivering it to the organs and tissues of your body. Blood pressure is measured in millimeters of mercury (mm Hg). A blood pressure reading is made up of two numbers: Systolic. This is the first number of your blood pressure reading. It’s the pressure placed on your arteries when your heart beats. Diastolic. This is the second number of your blood pressure reading. It measures the pressure on your arteries between heartbeats. Now let’s look at what’s a normal blood pressure reading and what’s considered high.

Blood pressure readings explained

• Normal. A reading of less than 120/80 mm Hg is considered normal.
• Elevated. A reading between 120–129 mm Hg systolic and above 80 mm Hg diastolic is considered elevated. You may be at risk of developing hypertension if you don’t take some steps to manage your blood pressure.
• Hypertension Stage 1. This is a reading between 130–139 mm Hg systolic or 80–89 mm Hg diastolic. Your doctor may recommend lifestyle changes or blood pressure medications, depending on your risk level for heart disease.
• Hypertension Stage 2. This is a reading that’s consistently measured at 140/90 mm Hg or higher. At this stage, your doctor will prescribe blood pressure medications and instruct you to make lifestyle changes.
• High blood pressure crisis. A reading of 180/120 mm Hg is considered to be dangerously high and requires immediate medical attention.

What is the best position to sleep in with high blood pressure?

Sleeping on the left side is the best sleeping position for hypertension because it relieves blood pressure on blood vessels that return blood to the heart.

Does your blood pressure change when you lie down?

It’s known changing positions can impact your blood pressure reading. However, there’s some disagreement about whether readings are higher or lower when you’re lying down. Several sources found that blood pressure was higher among study participants while they were lying down compared to sitting. One of these, a 2008 study included 6,485 healthy volunteers. However, the results of several newer studies have suggested blood pressure may be lower while lying down than when sitting: A 2017 study of 967 men and 812 women looked at the effect of body position on blood pressure. It found that diastolic readings were higher in both sexes when sitting but only on the first reading. Repeated blood pressure readings didn’t find the same difference between sitting and lying down. A study from 2018 investigated blood pressure readings in a cohort of 1,298 men. It found that both systolic and diastolic blood pressure readings were significantly higher in the seated position than when lying down. A 2017 study of 280 people with high blood pressure found that the average systolic and diastolic blood pressure readings were lower when measured while lying down than when measured in a sitting position. It’s important to note that the participants in this study had their blood pressure taken after resting for 10 minutes, which may have influenced the readings. Lower blood pressure while lying down makes sense when you think of your heart as a pump. When you’re lying down, most parts of your body are at the same level as your heart. Because of this, your heart doesn’t have to work as hard to circulate blood throughout your body.

So why are there variations in the findings, especially with the older studies?

Investigators suggest that the variations could be due to differences in the populations studied, such as age or underlying health conditions. The technique and order of the blood pressure measurements could also play a role. Although there may be minor changes based on your body position, there’s currently no consensus in the medical community that blood pressure is significantly lower or higher in one position over another. The only exception may be in situations where someone has an underlying health condition. For consistency, medical experts suggest that your blood pressure readings should always be taken in the same position. This makes it easier to compare your readings and to notice any changes.

What to know about blood pressure changes when you move from one position to another

Your blood pressure can also change as you move from one position to another. This may be particularly noticeable when you move from a sitting or lying position to a standing position. When you stand, gravity causes blood to pool in your lower body. This can cause a temporary drop in blood pressure. However, your body has a way to adjust to this change. Certain reflexes in your body send a signal to your brain when a drop in blood pressure is detected. Your brain then tells your heart to beat faster in order to pump more blood. This works to stabilize your blood pressure. However, sometimes this process can be interrupted, causing the drop in blood pressure to last longer than normal. When this happens, there’s a delay in blood flow to your brain. As a result, you may feel lightheaded, dizzy, or faint for a short while after you stand. This condition is called orthostatic hypotension or postural hypotension. It can be caused by a variety of factors, including:

• dehydration or overheating
• low blood sugar (hypoglycemia)
• medications, including blood pressure medications, certain types of antidepressants, and medications used to treat Parkinson’s disease
• heart conditions, such as heart valve problems, slow heart beat (bradycardia), and heart failure
• nervous system conditions like Parkinson’s disease or multiple system atrophy
• endocrine system conditions, such as thyroid disease and Addison’s disease