Common Blood Pressure Measurement Mistakes

Blood pressure responds to almost everything: posture, conversation, a cup of coffee, even a full bladder. That sensitivity means small mistakes during measurement can produce readings that are misleadingly high or low. Most are easy to correct once you know about them.

Preparation mistakes

1. Measuring straight after activity, food or caffeine

Exercise, meals, caffeine and tobacco all affect blood pressure for a while afterward. The CDC advises not eating or drinking anything for 30 minutes before measuring. Many guidelines add caffeine, smoking and exercise to that list.

2. Not resting first

Walking to the chair and measuring immediately captures an active reading. Sit quietly for at least five minutes.

3. A full bladder

Needing the bathroom can push readings up. Go first.

Posture mistakes

4. Back not supported

Sitting on a stool or the edge of a bed makes the body work to hold itself upright. Use a chair with a back.

5. Legs crossed or feet dangling

Crossing the legs can raise the reading. Keep both feet flat on the floor.

6. Arm unsupported or at the wrong height

If the arm hangs by your side or is held up by its own muscles, the reading changes. Rest the arm on a table so the cuff is at chest height.

Cuff mistakes

7. Wrong cuff size

A cuff that is too small tends to read high; one that is too large tends to read low. Measure your arm and check the cuff’s range. If you need a larger size for our monitor, see the Upper Arm Cuff, Large.

8. Cuff over clothing

Fabric interferes with the measurement, and a rolled-up tight sleeve acts like a tourniquet. Place the cuff on bare skin.

9. Cuff too loose, too tight or misplaced

The cuff should be snug, about an inch above the elbow crease, with the marker positioned as the instructions describe.

Behavior mistakes

10. Talking, texting or moving

Conversation and movement raise blood pressure and can cause errors. Stay still and silent until the result appears.

Method mistakes

• Taking only one reading. Take at least two, one to two minutes apart.
• Measuring at random times. Readings taken at the same times each day are comparable.
• Measuring repeatedly when anxious. Checking again and again after a high reading often drives the numbers up. Rest, breathe and retest after a few minutes.
• Switching arms. Use the same arm each time unless told otherwise.
• Discarding readings you do not like. Record everything; your doctor needs the true picture.

Equipment mistakes

• Using an unvalidated device. Choose a monitor that has been independently validated.
• Low batteries. Weak batteries can cause errors.
• Never checking the monitor. Take it to an appointment periodically for comparison.
• Relying on wrist readings without positioning the wrist at heart level.

Interpretation mistakes

• Panicking over one high reading. Blood pressure fluctuates. Look at averages over several days.
• Changing medicines yourself. Never adjust or stop treatment on the basis of home readings without medical advice.
• Ignoring consistently high readings. If your average is above the target your doctor has set, make an appointment.
• Ignoring very high readings with symptoms. A reading above 180/120 mm Hg with chest pain, breathlessness, weakness, vision changes or difficulty speaking is an emergency.

A quick self-check before each reading

• Have I rested for five minutes?
• Is my back supported and are my feet flat?
• Is my arm supported at chest height?
• Is the cuff on bare skin and the right size?
• Am I silent and still?

The bottom line

Good technique costs nothing and makes your readings trustworthy. Fix the posture, the cuff and the timing, and record every result. Find a Blood Pressure Log Book and other accessories in our heart and blood pressure department.

Sources

1. Centers for Disease Control and Prevention. Measuring Your Blood Pressure.
2. British Heart Foundation. How to measure your blood pressure at home.
3. American Heart Association. Understanding Blood Pressure Readings.
4. NHS. Blood pressure test.