A blood pressure of 109/66 is a good reading. It falls squarely within the normal range, which is defined as below 120/80 mmHg, and it sits comfortably above the low blood pressure threshold of 90/60 mmHg. For most adults, this is exactly where you want to be.
Where 109/66 Falls on the Scale
Blood pressure is measured in two numbers. The top number (systolic) reflects the pressure in your arteries when your heart beats. The bottom number (diastolic) measures the pressure between beats, when your heart is resting. Both numbers matter.
The American Heart Association and American College of Cardiology break blood pressure into categories:
- Normal: Below 120/80 mmHg
- Elevated: 120–129 systolic with diastolic below 80
- Stage 1 hypertension: 130–139 systolic or 80–89 diastolic
- Stage 2 hypertension: 140/90 mmHg or higher
- Hypotension (low blood pressure): Below 90/60 mmHg
At 109/66, both your systolic and diastolic numbers are in the normal category. The most recent 2025 AHA/ACC guidelines encourage most adults to aim for below 120/80, so your reading is right on target. You don’t need to take any special action to change it.
Why the Diastolic Number Might Seem Low
Some people see 66 on the bottom and wonder if that’s too low. It isn’t. Diastolic readings only become a clinical concern when they drop below 60 mmHg, and even then, only if symptoms are present. A diastolic of 66 is perfectly healthy.
That said, blood pressure fluctuates throughout the day. It rises during physical activity, stress, and even conversation, and dips during sleep or periods of deep relaxation. A single reading is a snapshot. If you’re monitoring at home, taking readings at the same time each day over a week or two gives a much more reliable picture than any one measurement.
Home Monitors and Accuracy
If you took this reading on a home blood pressure cuff, it’s worth knowing that these devices have a built-in margin of error. The international validation standard considers a device acceptable if it’s within 10 mmHg of the true value at least 85% of the time. That means your actual blood pressure could reasonably be a few points higher or lower than 109/66. Even accounting for that range, you’d still be well within normal limits.
For the most accurate home readings, sit with your back supported and feet flat on the floor. Rest for five minutes before measuring. Keep the cuff on bare skin at heart level, and avoid caffeine or exercise for 30 minutes beforehand.
When a Reading Like This Is Especially Common
Certain groups tend to run on the lower end of normal. People who exercise regularly, particularly in endurance sports like running, cycling, or swimming, often have resting blood pressures in the 100–115 systolic range. A study of nearly 3,700 young athletes found that those in dynamic sports (endurance and speed-based activities) had noticeably lower resting blood pressure than those in more static, strength-based sports.
Blood pressure also tends to run lower during pregnancy, particularly in the first and second trimesters, before rising again closer to delivery. A reading of 109/66 during pregnancy is normal and not a cause for concern on its own.
Younger adults and people with smaller body frames frequently have readings in this range as well. It’s simply their baseline.
Signs That Low-Normal Becomes Too Low
A blood pressure of 109/66 is not low. But if your readings trend downward over time, or you start noticing certain symptoms, it’s useful to know what to watch for. Most healthcare professionals only consider blood pressure “too low” when it causes symptoms. The numbers alone don’t tell the full story.
Symptoms of problematic low blood pressure include:
- Dizziness or lightheadedness, especially when standing up
- Blurred or fading vision
- Fatigue that doesn’t improve with rest
- Trouble concentrating
- Fainting or near-fainting episodes
- Nausea
If you feel fine at 109/66, your body is circulating blood effectively and your organs are getting what they need. No symptoms means no problem. The clinical threshold for hypotension is a systolic reading below 90 or a diastolic below 60, and your numbers are well above both.
What to Do With a Good Reading
The short answer: keep doing what you’re doing. A reading of 109/66 suggests your cardiovascular system is functioning well. The habits that maintain healthy blood pressure are the ones you’ve likely heard before: regular physical activity, a diet that isn’t heavily processed or salt-heavy, adequate sleep, and moderate alcohol intake if you drink at all.
Checking your blood pressure periodically is still worthwhile even when readings are normal. Blood pressure tends to rise gradually with age, and catching an upward trend early gives you the chance to adjust lifestyle factors before medication ever enters the conversation. Once or twice a year is plenty if your numbers are consistently in this range.