Why should caffeine or nicotine be avoided before BP measurement?

• A. They lower blood pressure.
• B. They do not affect blood pressure.
• C. They cause tachycardia but no BP change.
• D. They acutely raise blood pressure and can bias readings.

Answer: (D)

Caffeine and nicotine act as stimulants that activate the sympathetic nervous system, causing blood vessels to constrict and the heart to work harder. This produces a temporary increase in both systolic and diastolic blood pressure (often with a faster heart rate). Because blood pressure is meant to reflect a person’s usual level rather than a short-term spike, consuming caffeine or nicotine before measurement can bias the result and make the reading appear higher than normal. To obtain an accurate measurement, it’s typical to avoid these substances for a period before taking the reading, along with ensuring the patient rests quietly in the proper position.