How to Use the Blood Pressure Accuracy Guide
Blood pressure can vary by tens of mmHg depending on when and how it's measured. Select your measurement time slot and what you did before measuring to get a reliability score and specific guidance.
According to the American Heart Association (AHA), the best home BP reading is taken in the morning before medications, eating, or exercising, after sitting quietly for 5 minutes. An evening reading before bed adds useful context. Taking two readings and averaging them is recommended practice.
Caffeine can temporarily raise blood pressure by 5–10 mmHg, and smoking can raise it by up to 30 mmHg for 20–30 minutes. Accurate BP monitoring requires consistent measurement conditions day over day.
Frequently Asked Questions
This is called "white coat hypertension" — anxiety in a clinical setting temporarily raises BP. Home readings are often more representative of your true baseline. If home readings are consistently normal but clinic readings are high, mention this to your doctor.
A difference of up to 10 mmHg between arms is normal. A difference of 20 mmHg or more may indicate a circulatory issue and warrants medical evaluation. Always use the same arm (whichever reads higher) for consistent tracking.
Morning BP should be measured before taking blood pressure medication so you see your baseline without drug effects. Evening measurements can be taken regardless of medication timing, as long as you're at rest.