A blood pressure of 115/66 mmHg is a good reading. It falls squarely in the “normal” category, which is defined as a systolic (top number) below 120 and a diastolic (bottom number) below 80. Both of your numbers sit comfortably within that range, placing you in the healthiest blood pressure category recognized by major medical guidelines.
Where 115/66 Falls on the Scale
The most recent 2025 guidelines from the American Heart Association and American College of Cardiology use four categories for adult blood pressure:
- Normal: below 120/80 mmHg
- Elevated: 120 to 129 systolic with diastolic still below 80
- Stage 1 hypertension: 130 to 139 systolic or 80 to 89 diastolic
- Stage 2 hypertension: 140 or higher systolic, or 90 or higher diastolic
At 115/66, you’re not even close to the elevated range. These categories apply to all adults regardless of age. The 2017 guideline update eliminated separate thresholds for people over 65, so the same standards hold whether you’re 30 or 75.
What This Means for Heart Disease Risk
Cardiovascular risk rises in a predictable, dose-like pattern as blood pressure climbs. Starting at 115/75, the risk of heart disease and stroke doubles with every increase of 20 points systolic or 10 points diastolic. That means someone at 135/85 faces roughly double the cardiovascular risk of someone at 115/75, and someone at 155/95 faces roughly four times the risk.
Your reading of 115/66 sits right at the bottom of that risk curve. It’s essentially the baseline from which risk begins to increase. Maintaining blood pressure in this range long term is one of the strongest protections against heart attack, stroke, and kidney disease.
Is the Diastolic Number Too Low?
A diastolic reading of 66 is healthy. Normal diastolic pressure is anything below 80, and 66 is well within that window. There’s no official lower cutoff for blood pressure in people who feel fine. Some people naturally run on the lower side, and that’s perfectly normal as long as they aren’t experiencing symptoms.
Symptoms of blood pressure that’s too low include dizziness or lightheadedness, fainting, blurry vision, unusual fatigue, nausea, and feeling confused or foggy. Older adults are particularly prone to drops in blood pressure when standing up or after meals, which can cause falls. If you’re not experiencing any of these issues, a diastolic of 66 is nothing to worry about.
Why Accuracy Matters
A single reading only tells you so much. Blood pressure fluctuates throughout the day based on stress, caffeine, physical activity, and even the position of your body. To know your true baseline, the CDC recommends a consistent measurement routine:
- Sit with your back supported for at least 5 minutes before taking a reading.
- Keep both feet flat on the floor with legs uncrossed.
- Rest your arm on a table so the cuff sits at chest height.
- Stay quiet during the measurement. Talking can raise your reading.
- Take at least two readings one to two minutes apart, then average them.
If you got your 115/66 reading at a pharmacy kiosk while rushing through errands, it may not reflect your resting blood pressure. A reading taken at home under calm, controlled conditions is more reliable. Over time, tracking several readings gives you a much clearer picture than any single number.
Keeping Your Blood Pressure in This Range
The overall treatment goal in the 2025 guidelines is to stay below 130/80. You’re already well under that threshold. The habits that help maintain healthy blood pressure are straightforward: regular physical activity, a diet rich in fruits, vegetables, and whole grains while limiting sodium, maintaining a healthy weight, managing stress, limiting alcohol, and not smoking. These aren’t just relevant to people with high blood pressure. They’re what keeps normal readings normal as you age.
Systolic pressure tends to creep upward over the years as arteries stiffen and plaque accumulates. A reading of 115/66 today doesn’t guarantee the same number in a decade, but it does mean you’re starting from a strong position. Checking your blood pressure periodically, even once every few months at home, helps you catch any upward trend early before it crosses into a category that needs intervention.