A good bottom number for blood pressure is below 80 mm Hg. That threshold, confirmed in the latest 2025 AHA/ACC guidelines, separates normal diastolic pressure from Stage 1 hypertension. But the bottom number can also be too low, and understanding the full range helps you know where you stand.
What the Bottom Number Measures
Your blood pressure reading has two numbers. The top number (systolic) captures the force when your heart contracts. The bottom number (diastolic) measures the pressure in your arteries between beats, when your heart is resting and refilling with blood. This resting pressure matters because it’s when your heart muscle itself receives most of its blood supply. When diastolic pressure drops too low, the heart can be starved of oxygen. When it stays too high, it damages blood vessel walls over time.
The Ranges That Matter
Current guidelines break diastolic pressure into clear categories:
- Normal: below 80 mm Hg
- Stage 1 hypertension: 80 to 89 mm Hg
- Stage 2 hypertension: 90 mm Hg or higher
Notice that “elevated blood pressure” (when the top number sits between 120 and 129) still requires a bottom number below 80 to qualify for that category rather than full hypertension. In other words, once your diastolic hits 80, you’ve crossed into high blood pressure territory regardless of what the top number says.
These thresholds apply across age groups. Earlier guidelines used a more relaxed target of 150/80 for adults 65 and older, but the current framework treats the 80 mm Hg diastolic cutoff the same for all adults.
When the Bottom Number Is Too Low
While below 80 is the goal, there’s a floor. Blood pressure is generally considered low at a reading under 90/60 mm Hg. A diastolic number in the low 60s or below starts to raise concern, particularly for heart health. Research from Johns Hopkins has identified increased risk of coronary events when diastolic pressure falls below 60 to 70 mm Hg. At that level, the heart muscle may not receive enough blood flow during its resting phase, which can lead to subtle damage over time.
Most doctors consider low blood pressure a problem only when it causes symptoms. Those symptoms include dizziness, lightheadedness, blurred vision, fatigue, and trouble concentrating. If you regularly see diastolic readings in the 50s and feel fine, that may simply be your normal. But if those numbers come with any of these symptoms, it’s worth investigating.
So the practical sweet spot for the bottom number is roughly 60 to 79 mm Hg. Below 60 carries its own risks; at 80 or above, you’re in hypertension range.
Why a High Bottom Number Matters on Its Own
It’s possible for your bottom number to be elevated while your top number stays normal. This is called isolated diastolic hypertension, defined as a diastolic reading of 80 mm Hg or higher with a systolic reading below 130. It’s easy to dismiss because the top number looks fine, but it carries real consequences. People with this pattern face a higher risk of heart failure and are more likely to die from cardiovascular disease. These risks are greatest for women and people under 60.
If your bottom number consistently sits in the 80s while your top number is in the 110s or 120s, don’t assume everything is fine just because the top number looks healthy.
Getting an Accurate Reading
Before worrying about your numbers, make sure they’re reliable. A poorly fitting blood pressure cuff is one of the most common sources of error. The inflatable portion should cover 75% to 100% of the distance around your upper arm, and the cuff width should span 40% to 80% of the length from your elbow to your shoulder. A cuff that’s too small will give artificially high readings, which could make a normal diastolic number look elevated.
If you check at home, take two readings each time with a one-minute pause between them. A single reading can be thrown off by caffeine, a full bladder, or simply rushing to sit down. Patterns over multiple readings matter far more than any individual number.
Lowering a High Bottom Number
Lifestyle changes can meaningfully move both blood pressure numbers. The most impactful single change is dietary: eating a diet rich in whole grains, fruits, vegetables, and low-fat dairy while cutting saturated fat can lower blood pressure by up to 11 mm Hg. Reducing sodium intake to 1,500 mg per day or less can drop it another 5 to 6 mm Hg.
Regular aerobic exercise, such as brisk walking, cycling, or swimming, lowers blood pressure by about 5 to 8 mm Hg. You don’t need intense workouts. Consistency matters more than intensity. Weight loss also contributes, with blood pressure typically falling about 1 mm Hg for every kilogram (roughly 2.2 pounds) lost.
Potassium plays a quieter but significant role. Getting 3,500 to 5,000 mg of potassium daily from foods like bananas, potatoes, beans, and spinach can lower blood pressure by 4 to 5 mm Hg. Most people don’t hit that target, so even modest increases can help. These changes work on both numbers, but they’re particularly useful if your diastolic reading is the one that’s crept above 80.