Yes, LSD raises blood pressure. The increase is temporary, typically peaking about one hour after ingestion and returning to normal within roughly 12 hours. In clinical studies of healthy volunteers, the highest recorded systolic reading was 173 mmHg and the highest diastolic was 103 mmHg. For most people in controlled settings, the rise is moderate and clinically non-significant, but the effect is real and consistent across studies.
How Much Blood Pressure Increases
In a placebo-controlled study of healthy adults, a standard dose of LSD (200 µg) pushed average peak systolic blood pressure to about 148 mmHg and diastolic to about 88 mmHg. For context, normal resting blood pressure sits around 120/80. So LSD can push systolic readings roughly 20 to 30 points higher than baseline, sometimes more.
Interestingly, the blood pressure increase does not appear to be strongly dose-dependent. Whether someone takes 50 µg or 200 µg, blood pressure tends to rise by a similar amount. This is different from heart rate and body temperature, which do climb more steeply at higher doses. Doses above 25 µg all produced statistically significant elevations in blood pressure in one study of 131 LSD administrations.
Heart Rate Changes
LSD also raises heart rate, and this effect is more clearly tied to dose. On placebo, average peak heart rate in one study was about 74 beats per minute. At 100 µg of LSD, it rose to around 83 bpm, and at 200 µg, it reached approximately 86 to 90 bpm. That’s a modest increase for most people, roughly 10 to 15 extra beats per minute.
About 15% of all LSD administrations in clinical trials produced tachycardia, defined as a heart rate above 100 bpm. The single highest heart rate recorded was 129 bpm. While that’s elevated, it’s comparable to what you might experience during moderate exercise or a stressful event.
Why LSD Affects the Cardiovascular System
LSD’s primary target in the brain is the serotonin 2A receptor, the same receptor responsible for its hallucinogenic effects. Stimulating this receptor activates the body’s sympathetic nervous system, the same “fight or flight” response that triggers during stress or physical exertion. That sympathetic activation raises heart rate, constricts blood vessels, dilates pupils, and bumps up body temperature.
There’s a second mechanism at play. LSD is derived from ergot alkaloids, a class of compounds known to activate receptors on blood vessel walls. These compounds latch onto the receptors tightly and dissociate slowly, which can cause prolonged constriction of blood vessels. This vasoconstrictive property is part of what drives the blood pressure increase and, in rare cases, can reduce blood flow to specific areas. At least one case report documented a young, previously healthy man who suffered an acute stroke from cerebral artery vasospasm shortly after taking LSD.
Timeline of Effects
Blood pressure and heart rate changes follow a predictable arc. They begin rising within minutes of ingestion, peak at roughly one hour, and gradually return to baseline over the course of about 12 hours. The cardiovascular effects track loosely with the subjective experience of the drug, though the psychological effects of LSD can last somewhat longer. By the time the experience is fully over, vital signs have generally normalized.
Risks for People With Heart Conditions
Clinical trials consistently describe the cardiovascular effects of LSD in healthy volunteers as “clinically non-significant,” meaning they don’t reach levels that would typically require medical intervention. But these studies specifically exclude people with pre-existing heart disease, high blood pressure, or other cardiovascular conditions. That selection bias is important: the reassuring safety data doesn’t necessarily apply to someone who already has elevated baseline blood pressure or compromised blood vessels.
For someone whose resting blood pressure is already 140/90, an additional 20 to 30 point spike in systolic pressure could push readings into a range associated with hypertensive urgency. Combined with LSD’s vasoconstrictive properties and its long duration of action (up to 12 hours of cardiovascular stimulation), the risk profile looks meaningfully different for anyone with underlying cardiovascular vulnerability.
Microdosing and Repeated Use
Microdosing typically involves taking roughly 10 to 20 µg of LSD, well below the threshold where significant blood pressure changes have been measured in clinical studies (above 25 µg). However, there is very little formal data on the cardiovascular effects of repeated low-dose LSD use over weeks or months. The existing clinical evidence covers single-dose administration in controlled settings, not chronic use patterns. One theoretical concern relates to LSD’s ergot-derived structure: drugs that repeatedly stimulate serotonin 2B receptors on heart valves have been linked to valvular heart disease in other contexts, though whether LSD microdosing carries this risk remains unconfirmed.