What Not to Do When Taking Your Blood Pressure at Home
The common mistakes, how much each can change your reading, and a free checklist to keep by your monitor.
Checklist PDF (US Letter)Checklist PDF (A4)
A home reading is only useful if it is measured well. Small habits can shift the number enough to change which category you appear to be in. These are the mistakes worth fixing first.
How much each mistake can change your reading
These estimates come from American Heart Association guidance published in 2018. They are rough, they vary between people, and they do not simply add together.
| Mistake | Possible effect on the top number | The fix |
|---|---|---|
| Cuff over clothing | 5 to 50 points | Put the cuff on bare skin |
| Full bladder | 10 to 15 points | Go to the bathroom first |
| Talking | About 10 points | Stay silent, no phone calls |
| Arm not supported | Up to about 10 points | Rest it on a table at heart level |
| Back or feet not supported | 6 to 10 points | Sit in a chair with your feet flat |
| Cuff too small | 2 to 10 points | Measure your arm and get the right size |
| Crossed legs | 2 to 8 points | Keep both feet on the floor |
What not to do before you measure
- Don't have caffeine, smoke or exercise in the 30 minutes before.
- Don't measure straight away. Sit quietly for at least 5 minutes first.
- Don't measure at random times. Use the same times each day so your readings can be compared.
What not to do with the result
- Don't rely on one reading. Take two, one minute apart, and write down both.
- Don't only record the good ones. A log with the high readings removed can mislead your doctor.
- Don't keep retesting until you like the number. Stick to two readings.
- Don't change your medication because of a reading. Talk to your doctor first.
Which arm should you use?
The American Heart Association says you can use either arm, and there is usually not a big difference between them. The cuff should sit on your upper arm with its bottom edge just above the bend of your elbow.
If a reading is above 180/120: wait at least 1 minute and measure again. If it is still that high, contact your healthcare professional right away. If you also have chest pain, shortness of breath, back pain, numbness, weakness, a change in vision or difficulty speaking, call emergency services.
Sources
Last updated October 31, 2026
This page is general information, not medical advice. Talk to your doctor about your blood pressure.