Lying down and measuring blood pressure normal sitting high may be due to the presence of upright hypertension or blood pressure measurement errors. Upright hypertension is associated with persistent constriction of small arteries caused by a variety of factors and is also seen in the early stages of essential hypertension. The diagnostic criteria for hypertension is a systolic blood pressure ≥140 mmHg and/or a diastolic blood pressure ≥90 mmHg on three occasions not taken on the same day. In addition, measurement errors can occur if blood pressure is measured in the wrong way while sitting, if the muscles of the arm are exerted during measurement, or if the rubber tube of the sphygmomanometer is bent or compressed. Blood pressure should be measured after a quiet, restful day, with the arm muscles relaxed and the sphygmomanometer at the same level as the arm being measured. If you have high blood pressure, you need to seek medical advice and reasonable treatment.