For measuring blood pressure, smartwatches use an optical heart rate sensor. It detects the time it takes for a pulse to travel from the heart to the wrist. It is also known as Pulse Transit Time (PTT), based on which it shows the blood pressure readings. If the blood pressure is high, the pulse transit time is faster, and if the blood pressure is low, the pulse transit time is slower. Measuring blood pressure is much harder than tracking heart rate and rhythm, and getting it right is arguably even more important. Having more ways to easily take blood pressure measurements at home could be a big benefit to people with hypertension (high blood pressure) or other concerns. Pressure measurement taken exclusively in a doctor’s office are often unreliable. Some people have higher blood pressure in-office because they’re anxious about the visit, while other people have masked hypertension – high blood pressure at home, but normal blood pressure at the doctor.

Use this checklist:

• Don’t eat or drink anything 30 minutes before you take your blood pressure.
• Empty your bladder before your reading.
• Sit in a comfortable chair with your back supported for at least 5 minutes before your reading.
• Put both feet flat on the ground and keep your legs uncrossed.
• Rest your arm with the cuff on a table at chest height.
• Make sure the smart watch is snug but not too tight. The watch should be against your bare skin, not over clothing.
• Do not talk while taking your blood pressure.