Blood pressure low pressure higher than 90mmHg may cause headache. The normal range of low blood pressure is 60~90mmHg, low pressure higher than 90mmHg may be suffering from hypertension, high blood pressure may lead to abnormal expansion of intracranial blood vessels, diastolic dysfunction and increased intracranial pressure, causing headache, nausea, fatigue and other symptoms. Prolonged low blood pressure higher than 90mmHg will also form micro-aneurysms in the brain, micro-aneurysm rupture triggered cerebral hemorrhage can also cause headache symptoms. High blood pressure is easily complicated by cerebral thrombosis, cerebral thrombus dislodgement and blockage of cerebral blood vessels occurring cerebral infarction, will also cause headache symptoms. Blood pressure higher than 90 mmHg may also have other risks or complications, such as heart failure, coronary heart disease, chronic renal failure, retinopathy and so on. If you find that your blood pressure is higher than 90 mmHg, you should go to the hospital in time and make lifestyle adjustments or use appropriate antihypertensive medication to control your blood pressure under the guidance of your doctor to avoid further progression of your condition.