Adults only (18+)

Does THC Affect Blood Pressure?

As cannabis use becomes more common in both medical and recreational settings, questions are being raised about its effect on the heart and circulation. One area of concern is blood pressure. THC, the primary psychoactive compound in cannabis, is known to influence the nervous system. But does it raise or lower blood pressure? And is it safe for people with cardiovascular conditions?

This article is for anyone using cannabis or THC-based products, especially those with high or low blood pressure, heart conditions, or general concerns about how cannabis might affect their circulation. Using research from trusted UK health sources, we’ll explain what is currently known about the impact of THC on blood pressure.

How THC Interacts with the Body

THC, or tetrahydrocannabinol, acts on the body’s endocannabinoid system, which plays a role in regulating mood, appetite, pain and blood vessel function. THC binds to CB1 receptors in the brain and nervous system, causing a range of physiological changes, including altered heart rate and blood vessel dilation.

While cannabis is often associated with relaxation, THC can actually have stimulant-like effects depending on the dose, method of use and individual response. This includes possible changes in blood pressure.

Short-Term Effects on Blood Pressure

In the short term, THC can cause a drop in blood pressure immediately after use, known as postural or orthostatic hypotension. This can result in dizziness, light-headedness or fainting, particularly when standing up quickly after sitting or lying down.

At the same time, THC can increase heart rate, sometimes by 20 to 50 per cent above baseline. This is a natural response to the initial drop in blood pressure and is often temporary. The combination of reduced blood pressure and increased heart rate may feel unsettling, especially for first-time users.

Some users may experience a temporary spike in blood pressure before the drop occurs, depending on the method of use and their existing cardiovascular health. Smoking or vaping cannabis can deliver THC quickly into the bloodstream, intensifying these effects.

Long-Term Effects and Regular Use

There is currently limited evidence on the long-term impact of THC on blood pressure. Some studies suggest that regular cannabis use may be associated with small increases in blood pressure over time, while others show no significant effect or a potential reduction in blood pressure due to tolerance development.

It is important to note that cannabis is often smoked with tobacco, which independently raises blood pressure and increases cardiovascular risk. Therefore, studies involving smokers may not accurately reflect the isolated effect of THC.

Risks for People with High Blood Pressure

If you have high blood pressure, also known as hypertension, using THC-containing products could pose certain risks. Rapid changes in heart rate or blood pressure may increase the strain on the cardiovascular system, especially in older adults or those already on blood pressure medication.

The NHS and British Heart Foundation recommend caution when using substances that can affect heart rate or blood pressure. People with heart disease or a history of stroke should consult a medical professional before using THC, especially in higher doses or unregulated forms.

Low Blood Pressure and THC

For those with low blood pressure, THC may intensify symptoms such as dizziness, fatigue and fainting. The risk is higher when using high-strength products or when consuming cannabis in hot weather or without adequate hydration.

How Method of Use Matters

The way you consume THC can affect its impact on blood pressure. For example:

Smoking or vaping delivers THC quickly and may lead to sudden drops in pressure
Edibles take longer to take effect but can produce longer-lasting and stronger responses
Oils or tinctures allow for more controlled dosing but can still affect circulation
Topical products are unlikely to have a significant systemic effect on blood pressure

Understanding the strength and delivery method of your product can help you manage potential risks and avoid unpleasant side effects.

CBD vs THC: Are the Effects Different?

Unlike THC, CBD (cannabidiol) is non-intoxicating and may have more stable effects on blood pressure. Some studies suggest that CBD may lower blood pressure slightly in response to stress, although findings are still inconclusive.

Many users take combined CBD-THC products to balance the psychoactive effects of THC. However, these products still require caution, particularly for individuals with existing cardiovascular concerns.

What Do UK Regulations Say?

In the UK, THC is a controlled substance under the Misuse of Drugs Act 1971. Medical cannabis products containing THC are only available via prescription and are subject to strict safety and dosage standards.

CBD products sold over the counter must contain less than 1mg of THC per container. These products are not generally associated with blood pressure changes unless used in very large quantities or alongside other medications.

Should You Be Concerned?

For healthy individuals, occasional THC use in moderate amounts is unlikely to cause long-term harm to blood pressure. However, for people with known cardiovascular issues, arrhythmias, or high or low blood pressure, it is advisable to approach THC with caution.

Before using cannabis-based products, especially if you take blood pressure medication or have a heart condition, consult your GP or specialist. This is especially important if you experience dizziness, rapid heartbeat or chest pain during or after use.

Conclusion

THC can affect blood pressure in both directions, often lowering it shortly after use while simultaneously raising heart rate. For most healthy adults, these effects are temporary and manageable. However, people with cardiovascular conditions or those using cannabis frequently should monitor their response carefully and speak to a healthcare professional if concerned.

Understanding your own health status, using regulated products and starting with low doses can help you enjoy THC-based products more safely and responsibly.