A blood pressure of 104/66 mmHg is a good reading. It falls squarely in the “normal” category under the 2025 guidelines from the American Heart Association, which define normal blood pressure as below 120/80 mmHg. Both your top number (systolic) and bottom number (diastolic) are well within the healthy range, and this reading puts you far from any hypertension threshold.
Where 104/66 Falls on the Scale
The current blood pressure categories for adults are straightforward:
- Normal: below 120 systolic and below 80 diastolic
- Elevated: 120 to 129 systolic and below 80 diastolic
- 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 104/66, you’re 16 points below the threshold where blood pressure starts to become a concern. These categories apply the same way regardless of age or sex.
Is 104/66 Too Low?
Low blood pressure, or hypotension, is clinically defined as a reading below 90/60 mmHg. Your reading of 104/66 sits comfortably above that cutoff. Most healthcare professionals only consider blood pressure “too low” when it causes symptoms, not based on the number alone. What counts as normal for one person can feel low for another, so the number is only part of the picture.
If you feel fine at 104/66, there’s nothing to be concerned about. Many healthy adults, particularly those who exercise regularly, naturally run on the lower end of normal. During pregnancy, blood pressure also tends to dip in the first and second trimesters as hormonal changes relax blood vessels, so a reading like this can be especially common during early pregnancy.
Signs that your blood pressure might actually be too low for your body include dizziness or lightheadedness, blurred vision, fatigue, trouble concentrating, fainting, or an upset stomach. A sudden drop of even 20 mmHg from your usual reading can trigger these symptoms, even if the resulting number still looks “normal” on paper. So if you typically run around 120/80 and suddenly read 104/66, pay attention to how you feel.
What Your Diastolic Number Tells You
The bottom number, 66 in your case, reflects the pressure in your arteries between heartbeats. For most healthy adults, a diastolic reading in the 60s is perfectly fine. Research on cardiovascular outcomes suggests that around 70 mmHg is an optimal diastolic target, and readings above 60 generally carry no added risk.
Where diastolic pressure becomes more relevant is in older adults with stiff arteries. In that population, a diastolic reading consistently at or below 60 has been linked to worse cardiovascular outcomes, likely because the heart and organs aren’t getting enough blood flow during the resting phase between beats. At 66, you’re above that threshold, but it’s worth knowing that diastolic pressure matters more as you age.
Keeping a Good Reading
A reading of 104/66 reflects healthy cardiovascular function, and the habits that maintain it are the same ones you’ve probably heard before: regular physical activity, a diet that isn’t heavy on sodium or processed foods, maintaining a healthy weight, managing stress, and limiting alcohol. These factors have the biggest influence on where your numbers land over time.
Keep in mind that a single blood pressure reading is a snapshot. Blood pressure fluctuates throughout the day based on activity, stress, hydration, caffeine, and even the position of your arm during the measurement. If you’re tracking your numbers at home, take readings at the same time of day, sit quietly for five minutes beforehand, and average several readings over a week to get a reliable picture. That average matters more than any individual number.