A diagnosis of hypertension is not made on a single reading. It requires repeated measurements on at least two occasions, and preferably confirmation by home measurement or 24-hour recording — the thresholds for which are lower than for office measurement.
Classification of office blood pressure
| Category | Systolic | Diastolic | |
|---|---|---|---|
| Optimal | < 120 | and | < 80 |
| Normal | 120–129 | and/or | 80–84 |
| High normal | 130–139 | and/or | 85–89 |
| Grade 1 hypertension | 140–159 | and/or | 90–99 |
| Grade 2 hypertension | 160–179 | and/or | 100–109 |
| Grade 3 hypertension | ≥ 180 | and/or | ≥ 110 |
| Isolated systolic hypertension | ≥ 140 | and | < 90 |
Thresholds for different measurement methods
Measurement technique
Faulty measurement technique is the most common cause of misclassification.
- Five minutes' seated rest, back and arm supported, legs uncrossed, no conversation
- Cuff width ≥ 40% of the upper arm circumference — a cuff that is too narrow gives a falsely high reading
- The cuff at heart level
- Measure in both arms at the first visit; a difference > 15 mmHg suggests vascular disease, and the arm with the higher reading is used thereafter
- Two to three measurements one minute apart, taking the mean of the last two
- Orthostatic testing after 1 and 3 minutes of standing in older patients, patients with diabetes and anyone with dizziness
Definitions
White-coat hypertension: a raised office reading but normal readings at home or on 24-hour recording. Masked hypertension: normal in the office but raised outside it — associated with the same risk as manifest hypertension. Non-dipping: a nocturnal fall in pressure of < 10% of the daytime value; an independent risk marker.
Treatment targets
| Group | Systolic target | Diastolic |
|---|---|---|
| Adults 18–64 years | 120–130 | 70–79 |
| ≥ 65 years | 130–139, if tolerated | 70–79 |
| Diabetes | 120–130 | 70–79 |
| Chronic kidney disease | 130–139 | 70–79 |
Avoid a systolic pressure < 120 mmHg and a diastolic pressure < 70 mmHg on treatment — the benefit plateaus and adverse effects increase.
Hypertensive crisis
Hypertensive urgency: markedly raised pressure without organ involvement — lower it orally over days. Hypertensive emergency: raised pressure with acute organ damage (encephalopathy, pulmonary oedema, aortic dissection, acute renal failure, pre-eclampsia) — intravenous treatment with a controlled reduction, as a rule no more than 25% during the first hour. The exception is aortic dissection, where a systolic pressure below 120 mmHg and a heart rate below 60 are the immediate goals.
