A systolic reading of 108 mmHg falls well within the range most clinicians consider normal and healthy. Standard guidelines define high blood pressure as 130/80 mmHg or above, and “low blood pressure” (hypotension) typically enters the conversation only when systolic pressure drops below about 90 mmHg or causes symptoms like dizziness and fainting. So for most people, 108 is not too low. But the number alone does not tell the whole story, because blood pressure is not a fixed value and context shapes whether any reading deserves attention.
What Blood Pressure Numbers Actually Tell You
A blood pressure reading has two parts. The top number (systolic) reflects the force your heart exerts when it pumps. The bottom number (diastolic) reflects the pressure in your arteries between beats, when the heart relaxes. Both matter independently. A large study examining over 1.3 million adult blood pressure readings found that sustained systolic pressure at or above 140 mmHg and diastolic pressure at or above 90 mmHg each independently predicted cardiovascular problems like heart attack and stroke.1Europe PMC. Effect of Systolic and Diastolic Blood Pressure on Cardiovascular Outcomes In other words, you cannot ignore one number just because the other looks fine.
For a systolic reading of 108, the more useful question is what the diastolic number is doing alongside it. A reading of 108/70 looks very different from 108/50. A diastolic number below about 60 mmHg in combination with a normal-ish systolic value can sometimes signal that blood is not perfusing organs well during the resting phase of the heartbeat. But 108/70, 108/68, or similar readings are entirely unremarkable for most adults.
When “Normal” Blood Pressure Still Causes Symptoms
The medical definition of hypotension is somewhat arbitrary because what matters clinically is whether the pressure is adequate for you. Some people walk around with a systolic pressure in the low 90s and feel perfectly fine. Others feel lightheaded at 105 if they are used to running at 130. Doctors tend to worry less about a specific cutoff and more about whether you are experiencing symptoms: dizziness, blurred vision, nausea, fatigue, difficulty concentrating, or fainting. If your reading is 108 and you feel fine, it is almost certainly not a problem.
That said, a sudden drop to 108 from your usual 135 is a different situation from always reading around 108. A rapid decline of 20 or 30 mmHg can make you symptomatic even if the landing number looks normal on paper. This is why a single snapshot reading has limited value without knowing your baseline.
Why Blood Pressure Fluctuates Throughout the Day
Blood pressure is not a fixed trait like your height. It follows a circadian rhythm, rising in the morning after you wake and declining during sleep.2PubMed Central. Circadian Blood Pressure Rhythm in Cardiovascular and Renal Health and Disease The daily swing can be substantial. It is common for systolic pressure to vary by 10 to 20 mmHg over the course of a day depending on activity, stress, caffeine intake, temperature, and even how recently you ate. A reading of 108 taken first thing in the morning after a calm night may just be your sleeping pressure slowly climbing back to its daytime cruising altitude. Researchers continue to study how these daily rhythms interact with hypertension risk, and the functional impact of these biological rhythms is still being mapped out.3Circulation Research. Hypertension: Causes and Consequences of Circadian Rhythms in Blood Pressure
Posture matters too. When you stand up, gravity pulls blood toward your legs, temporarily reducing the volume returning to your heart. In healthy people, the nervous system quickly compensates by constricting blood vessels and nudging heart rate up.4The Lancet Neurology. Orthostatic hypotension: managing a complex, but common medical problem If you check your blood pressure while seated and relaxed, you might see 108. Check it again after standing quickly and it could read higher or lower, depending on how well that reflex is working.
Common Reasons Blood Pressure Runs on the Lower Side
If your readings consistently hover around 100 to 110 systolic, several everyday explanations are worth considering before anything exotic.
- Hydration status: Even mild dehydration can impair blood pressure regulation. When you lose fluid, blood volume decreases, stroke volume drops, and the body has to work harder to maintain pressure. Research shows that dehydration can reduce mean arterial pressure by several mmHg during upright activity and worsen the body’s ability to tolerate standing.5American Journal of Physiology-Heart and Circulatory Physiology. Supine exercise restores arterial blood pressure and skin blood flow despite dehydration and hyperthermia Acute dehydration also appears to reduce blood vessel function and increase sympathetic nervous system strain.6PubMed Central. Hydration Status and Cardiovascular Function
- Physical fitness: Well-conditioned athletes often have resting systolic pressures in the low 100s or even the 90s. A strong, efficient heart pumps more blood per beat, so it does not need as much pressure to get the job done. If you exercise regularly and your blood pressure is 108 with no symptoms, that is typically a sign of cardiovascular fitness, not a medical concern.
- Body size: Smaller-framed people tend to run lower pressures. This is partly a matter of physics: less tissue to perfuse, a shorter vascular tree, and proportionally smaller heart size.
- Eating: Blood pressure can dip after meals because blood flow is redirected to the digestive tract. This postprandial dip is usually mild in younger adults, but in older adults it can be more pronounced. The mechanism involves blood pooling in the gut, altered gastric emptying, and the activity of certain intestinal hormones.7Geriatrics & Gerontology International. Postprandial Hypotension—Methods for the Evaluation and Management
Medications That Can Push Blood Pressure Lower Than Expected
If you take medication for high blood pressure and your readings are now around 108, the treatment may be working a bit too aggressively. This is worth discussing with your prescriber, especially if you are feeling dizzy or tired. A study of patients with arterial disease found that being on three or more blood pressure medications was associated with worse physical and mental health status compared to being on none, independent of the blood pressure numbers themselves.8PubMed Central. Low blood pressure, antihypertensive treatment, and physical and mental health status in patients with arterial disease That does not mean the drugs are the sole cause of feeling poorly, but it does suggest that chasing ever-lower blood pressure targets with stacking medications can carry trade-offs.
Certain drug classes deserve particular attention. Peripheral vasodilators, including alpha-blocker medications and some types of calcium channel blockers, can worsen postural blood pressure drops and contribute to orthostatic hypotension, especially in older adults.9PubMed. Postural blood pressure changes and orthostatic hypotension in the elderly patient: impact of antihypertensive medications Blood pressure medications are not the only culprits, though. Antidepressants, drugs for Parkinson’s disease, prostate medications, and even some over-the-counter antihistamines can lower blood pressure as a side effect.
The J-Curve Problem and How Low Is Too Low
For a long time, the assumption in treating high blood pressure was simple: lower is better. But research over the past couple of decades has complicated that picture. Large clinical trials have observed what researchers call a J-curve, where cardiovascular risk drops as blood pressure comes down from high levels, but then starts to creep back up again if blood pressure falls below a certain floor. This floor appears to sit around a diastolic pressure of 70 to 80 mmHg and a systolic pressure somewhere below 120 to 130 mmHg.10PubMed Central. The significance of the j-curve in hypertension and coronary artery diseases
The SPRINT trial, one of the most influential blood pressure studies in recent years, found that targeting systolic pressure below 120 mmHg reduced cardiovascular events by about 25% compared to a target below 140 mmHg.11Hypertension. Systolic Blood Pressure Intervention Trial (SPRINT) and Target Systolic Blood Pressure in Future Hypertension Guidelines But even within that trial, researchers noticed that going too far below the target was associated with more adverse events and higher mortality.12Circulation. J Curve in Patients Randomly Assigned to Different Systolic Blood Pressure Targets The J-curve appeared for both treatment groups, with the lowest risk sitting just below whatever the target was.
What does this mean for you and a reading of 108? For a healthy person whose blood pressure naturally settles at 108, the J-curve is largely irrelevant because it primarily describes the risk of pushing already-treated blood pressure too low with drugs. But if you are on medication and your systolic pressure is consistently dipping into the low 100s with symptoms, the J-curve data suggests there may genuinely be a floor below which further reduction stops helping and starts causing harm. The mechanism is thought to involve reduced blood flow to the heart itself, since the coronary arteries fill mainly during diastole. Push diastolic pressure too low, and the heart muscle may not get enough oxygen between beats.
Sex, Age, and Individual Variation
Blood pressure is not one-size-fits-all, and what counts as “your normal” depends partly on your sex and age. Younger women in particular tend to run lower blood pressures than men of the same age. Research into the physiological reasons for this has revealed that in young women, the body’s blood-vessel-constricting signals are offset by opposing vasodilator mechanisms, effectively keeping blood pressure lower despite the same level of nervous system activity that would raise it in a young man.13Experimental Physiology. Sex differences and blood pressure regulation in humans As women age and these vasodilator mechanisms diminish, the relationship between nervous system drive and blood pressure becomes more direct, and pressures tend to rise.
In practical terms, a systolic reading of 108 in a 25-year-old woman is so common it barely warrants a comment. The same reading in a 75-year-old man who last year was running at 145 is a different conversation entirely. Context is everything.
Blood Pressure During Pregnancy
Pregnancy introduces its own blood pressure patterns. In many women, blood pressure dips during the second trimester before climbing back up toward the end of pregnancy. This mid-trimester drop is considered a normal part of the body adapting to the dramatically increased blood volume and expanding vascular system that support the growing fetus. However, the pattern is not universal. A prospective study found that a sizable portion of pregnant women did not experience this mid-trimester dip in systolic pressure, and factors like a family history of hypertension, obesity before pregnancy, and higher gestational weight gain were associated with the absence of the expected drop.14Oxford Academic (American Journal of Hypertension). Blood Pressure in Healthy Pregnancy and Factors Associated With No Mid-Trimester Blood Pressure Drop: A Prospective Cohort Study
If you are pregnant and seeing readings around 108, that is almost certainly within the expected range and not a cause for concern on its own. The time to flag a reading is when it drops low enough to cause dizziness or fainting, or when it suddenly rises in the third trimester, which can signal preeclampsia.
Could Your Reading Be Inaccurate?
Before worrying about a blood pressure number, it is worth asking whether the measurement itself was reliable. Home monitors are convenient but sensitive to technique. Cuff size, in particular, makes a meaningful difference. A study of automated blood pressure devices found that using a cuff that is too large for your arm can artificially lower the systolic reading by roughly 4 to 7 mmHg, while using a cuff that is too small can inflate the systolic reading by about 2 to 6 mmHg.15Blood Pressure Monitoring. Influence of cuff size on the accuracy of supine blood pressure measurement If you have slender arms and are using a standard-sized cuff, your reading of 108 might actually be a bit higher. If you have larger arms and are using a standard cuff, the true number could be lower than what you saw.
Other common sources of error include taking a reading right after exercise, talking during the measurement, sitting with your legs crossed (which can raise the number), having a full bladder, or resting the arm below heart level. If you got a single reading of 108 and are worried, retake it after five minutes of quiet sitting with your feet flat on the floor and your arm supported at chest height.
Orthostatic Hypotension and Autonomic Disorders
If your concern about blood pressure is not just a number on the screen but actual symptoms, particularly dizziness when standing, it is worth distinguishing between ordinary low-normal pressure and orthostatic hypotension. Orthostatic hypotension is formally defined as a sustained drop of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes of standing. It is not a disease itself but a sign that the cardiovascular reflexes responsible for compensating to gravity are not keeping up.
In many cases, the causes are benign and fixable: dehydration, prolonged bed rest, medication side effects, or heat exposure. Expert consensus recommends a stepwise approach: first review and adjust any medications that might be causing or worsening the drops, then try non-drug measures like increasing fluid and salt intake, wearing compression garments, and physical conditioning aimed at reducing venous pooling in the legs.16PubMed. Non-pharmacologic management of orthostatic hypotension
In a smaller number of cases, orthostatic hypotension has a neurological origin. When the autonomic nerves that control blood vessel tone are damaged or degenerating, the body simply cannot mount the reflexive constriction needed to keep blood pressure stable on standing. This is called neurogenic orthostatic hypotension, and it is linked to conditions like Parkinson’s disease, multiple system atrophy, pure autonomic failure, and diabetic autonomic neuropathy.17PubMed Central. Neurogenic orthostatic hypotension: pathophysiology, evaluation, and management These are all conditions where the nervous system’s ability to regulate involuntary functions breaks down. The common thread among several of these disorders is the abnormal accumulation of a specific protein in the nervous system, which damages the autonomic pathways responsible for blood vessel control.18PubMed Central. Neurogenic Orthostatic Hypotension: State of the Art and Therapeutic Strategies
If you are seeing readings around 108 only when standing and experiencing lightheadedness, near-fainting, or falls, that pattern deserves a medical evaluation even though 108 itself sounds innocuous. The issue is not the number in isolation but the drop it represents from your seated or lying-down pressure.
When to Bring It Up With a Doctor
A resting systolic reading of 108 in an otherwise healthy person who feels fine does not warrant medical attention. The situations that do warrant a conversation are relatively specific:
- New symptoms: Persistent dizziness, fatigue, blurred vision, or fainting episodes that coincide with lower-than-usual blood pressure readings.
- Medication changes: A noticeable drop in blood pressure following a new prescription or dose adjustment, especially blood pressure drugs, antidepressants, or prostate medications.
- Big shifts from baseline: If your pressure used to be 140 and is now 108, especially if you did not change any medications or habits, a clinician should evaluate what changed.
- Postural drops: Feeling woozy every time you stand, particularly if you are over 65 or have a neurological condition.
For everyone else, a reading of 108 is a number you can note and move on from. Blood pressure is a continuum, and the evidence consistently shows that the serious risks sit at the high end of the scale, not at 108.
Athletes, Endurance Training, and Low Resting Pressure
Endurance athletes frequently find their resting blood pressure sitting in the 100-to-110 range, and it is worth understanding why this happens rather than treating it as a medical oddity. Regular aerobic training remodels the heart. The left ventricle becomes slightly larger and more compliant, ejecting a greater volume of blood per beat. Because stroke volume increases, the heart can meet the body’s demands at a lower rate and lower pressure. This is the same adaptation that gives trained runners a resting heart rate in the 40s or 50s.
The practical concern for athletes is not the resting number but what happens under stress. A well-trained cardiovascular system should be able to ramp blood pressure up appropriately during exertion and recover quickly afterward. If an athlete is passing out during workouts or feeling lightheaded despite adequate hydration and nutrition, the issue is more likely related to overtraining, heat, or an underlying rhythm problem than to a resting systolic of 108. The low resting number, by itself, is almost universally a good sign in this population.