Normal blood pressure for a healthy 90-year-old, assuming that there is no unknown illness or health complications, ranges around 120/80 mmHg, according to Blood Pressure UK. Blood pressure varies between individuals depending on level of fitness, diet, hydration and current medications.
The ideal blood pressure for any healthy adult is 120/80 or less, reports Mayo Clinic. This indicates good health of the cardiovascular system and low risk for conditions such as heart attack or stroke. Blood pressure ranging from 120 to 139 systolic over 80 to 89 diastolic signifies prehypertension, and lifestyle changes are beneficial to the patient in controlling these numbers.
Blood pressure between 140 to 159 over 90 to 99 is classified as hypertension stage one, explains Mayo Clinic, and it represents the need for medical consult and lifestyle changes in order to prevent poor medical outcomes. Finally, blood pressure of 160/100 or more is classified as hypertension stage two, and indicates a higher risk of heart disease, heart attack and stroke, as well as the need for medical management of the condition.