Understanding blood pressure readings and FAQs

Blood pressure classifications were developed by the US Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pres­­sure; they apply to North American adult men and women who aren't currently taking antihypertensive medications and who aren't acutely ill. Here's a guide on understanding these classifications and maintaining a healthy blood pressure.

To determine the category you fall into, use the more elevated number in the reading: for example, if you have 140 mm Hg systolic and 100 mm Hg diastolic you would be in the Stage 2 category. Optimal

• Systolic ≤120 mm Hg
• Diastolic ≤80 mm Hg
• Recheck in two years.

Normal

• Systolic ≤130 mm Hg
• Diastolic ≤85 mm Hg
• Recheck in two years.

High-normal

• 130 to 130 mm Hg
• 85 to 89 mm Hg
• Recheck in one year.

Hypertension Stage 1 (Mild)

• 140 to 159 mm Hg
• 90 to 99 mm Hg
• Confirm within two months.

Stage 2 (Moderate)

• 160 to 179 mm Hg
• 100 to 109 mm Hg
• Undergo complete medical evaluation and/or begin treatment within one month.

Stage 3 (Severe)

• ≥180 mm Hg
• ≥110 mm Hg
•  Undergo complete medical evaluation and/or begin treatment immediately or within one week, depending on the severity of the hypertension.

Isolated systolic hypertension

• ≥140 mm Hg
• < 90 mm Hg
• Confirm within two months.

Q: Should I buy a home blood pressure monitor? 

A: It’s an excellent idea for anyone with hypertension to check their blood pressure at home. If you then average the results taken over several weeks, you'll get a much more accurate assessment of your real numbers than you will from measurements taken in the doctor’s office alone. (Lots of factors influence blood pressure, from time of day to diet and stress levels.) Keep a record so you and your doctor can discuss if your treatment plan is working. For an accurate reading, for 30 minutes before, have no caffeine, cigarettes or alcohol. Relax at least three to five minutes before starting your reading. Sit with your legs and ankles uncrossed. Wait two to three minutes before taking a second reading.

Q: Why does my blood pressure go up when I am in the mountains?

A: Even a modest rise in altitude will slightly increase your blood pressure — regardless of whether you have hypertension. This is a result of your body’s natural attempt to deal with lower amounts of oxygen available at higher elevations. During this process, complex changes occur throughout your body; you hyperventilate to get more oxygen, and your kidneys pump out hormones that constrict your blood vessels. Usually, your blood pressure will acclimate naturally, probably within 24 to 48 hours. If you're on medication and going above 1,800 metres (6,000 feet), ask your doctor whether you need to alter your normal dosage.

Q: Should I worry about low blood pressue?

A: The lower the better when it comes to blood pressure, but only as long as you feel good. If your pressure drops too low — a condition called hypotension — your health can be compromised. Hypotension can result from overly aggressive treatment of high blood pressure or other factors. The most common form, however, is postural hypotension, which occurs after you abruptly stand or sit up. Dizziness and fainting are common symptoms, the result of inadequate blood flow to the brain.If your doctor diagnoses postural hypotension, diet and lifestyle changes will probably be in order and medications will only be a last resort. Try to:

• Eat salty foods, especially in hot weather or when you're ill.
• Drink at least eight glasses of non-alcoholic beverages daily (sports drinks high in sodium and potassium are a good bet).
• Stretch your feet back and forth to stimulate their circulation before getting up from a prone or sitting position.
• Raise the head of your bed five to 20 degrees (bricks are helpful).