Question: What time of day should I measure my blood pressure if I am monitoring it myself?
Answer: Well, increasingly in the United States, and for that matter, globally, people are taking their blood pressures at home with devices purchased at a drugstore or the like. These devices can be acquired for well under 100 dollars, and technically are very sound. So, this creates a new layer of responsibility for the patient -- that is, taking the blood pressure at home provides additional information that a doctor can use.
The best time to take it typically is right before the next dose of your medication -- that's what's called a trough value. It shows you how well you have been controlled up to that point. Now, if I rephrase that just a little bit, if you take a pill in the morning, and you're going to take another pill in the evening, it's taking the blood pressure right before that second pill. Now the blood pressure's very much elevated at that point. Most times your doctor would instruct you, and even as a patient you would look at it logically, that you might take readings earlier than before that next dose, see how long the blood pressure medicine worked from that morning.
The other point about taking blood pressures at home that's very useful is: if you have symptoms, then it almost behooves you to take your blood pressure at the time of the symptom. Sometimes blood pressure medicines can lower blood pressure too much, and in that case, you'd like to attach a blood pressure to a symptom, and you might see a dosage adjustment, change in the time of day of dosing, but sometimes splitting medicines up given in morning and evening.