Home readings are only useful if they are taken consistently. Sit quietly for five minutes first, with your back supported, feet flat on the floor and legs uncrossed. Rest your arm on a table so the cuff sits at heart level, and place the cuff on bare skin rather than over a sleeve. Avoid caffeine, exercise and smoking for at least thirty minutes beforehand, and empty your bladder first, since a full bladder can raise a reading.
Take two readings one minute apart, morning and evening, and write down both. Do not talk or scroll your phone while the cuff inflates. Use a validated upper-arm monitor with a cuff that fits: a cuff that is too small can read falsely high. Bring your device to a clinic visit once so it can be compared against the clinic machine. If your readings stay at or above 130/80 across several days, share the log with your doctor rather than changing medication on your own.