Increase in haematocrit in borderline hypertensive men

1. Haematologic parameters were measured in untreated borderline hypertensive (BHT) men, and weight and age matched with normotensive men to determine whether previously described increased haematocrit (Hct) in established hypertension is evident in borderline hypertension. 2. Haematocrit was significantly increased in BHT men (mean 0.46, s.d. 0.032) compared with normotensive men (mean 0.43, s.d. 0.014) and correlated significantly with mean arterial pressure in this group (r = 0.67, P = 0.036) independent of weight. 3. The correlation of blood pressure with Hct in BHT men supports the concept that increased Hct may contribute to increased blood viscosity and thus to raised arterial pressure.