The body has numerous ways of adjusting blood pressure as needed to be sure its organs (primarily the brain) maintain a good supply of oxygen. This dynamic response is part of the reason some people have what is called white-coat hypertension. Being nervous in the medical office can result in a substantial increase in blood pressure that is not present at home. White-coat hypertension can make it difficult to get an accurate blood pressure measurement.
For the most accurate blood pressure measurement at a medical appointment, it’s best to sit quietly and rest for at least five minutes before having your blood pressure measured. Smoking and caffeine both raise blood pressure, so avoid both for at least an hour before your appointment. (Ideally, smoking should be avoided for life, so if you smoke, talk to your doctor about quitting if you haven’t already.)
When your blood pressure is measured, your arm should be at the level of your heart, and the blood pressure cuff should be sized appropriately for your arm. If the cuff just barely fits around your arm or pops off once it is in place, it may be too small, and you are likely to get a falsely elevated reading. Two readings are often sufficient at a medical visit, but at times, a reading taken at the end of the visit is most accurate because you are more relaxed.
It’s a good idea to write down your blood pressure readings taken at the doctor’s office, both for your own information, and to show to any other health-care providers you may see. This helps your health-care providers coordinate their care and see whether the measurements they’re getting are typical for you. It’s also important to discuss your blood pressure goal with the various members of your health-care team to be sure you’re all shooting for the goal established for people who have diabetes, less than 140/80 mm Hg. If you find that different members of your team have different goals in mind, you may need to take the lead in letting everyone know what your goal is.
Measuring your blood pressure at home is also very valuable, especially during periods of medication adjustments. Home blood pressure monitors typically cost about $40 to $60, and they are well worth the investment. Wrist monitors may not be as reliable as those that have a cuff that wraps around the upper arm. If you use a home blood pressure monitor, you should bring it to your doctor appointments periodically to be sure it is accurate. A good time to monitor at home is in the morning before you take any medicines. Early morning is when blood pressure tends to be highest and when the effects of some drugs are wearing off. It is also the highest risk period for stroke and heart attack.
Another tool that is often used to diagnose high blood pressure is the 24-hour ambulatory blood pressure monitor. This is a blood pressure monitor that is clipped onto a belt and connected to an arm cuff for a 24-hour period. Depending on how it is programmed, the cuff automatically inflates every 20–60 minutes to measure and record blood pressure throughout the day and night. It is a very useful tool to assess people with white-coat hypertension, difficult-to-control high blood pressure, or symptoms of low blood pressure (which may mean that a person’s high blood pressure is being overtreated). Measuring blood pressure while a person is asleep is important because blood pressure is expected to drop by about 10% to 20% at night. This is called a nocturnal dip. Absence of the nocturnal dip is associated with a higher risk of heart disease and stroke.
Types of high blood pressure
As stated earlier, the goal blood pressure for people with diabetes is less than 140/80 mm Hg consistently. That means the highest reading you should see is 139/79 mm Hg. Persistent readings above this target should prompt a focused evaluation of your blood pressure by you and your health-care team. The initial evaluation covers three major issues: identifying the cause of high blood pressure, looking for evidence of organ damage that may have already taken place, and discussing lifestyle issues that may be affecting blood pressure.