Can you donate plasma or blood if you smoke weed?

Medically reviewed by Codi Peterson, PharmD

Donating blood (Shutterstock)

Yes, you can donate blood and plasma if you use cannabis. However, there are some things you need to know before you go.

You cannot donate blood if you’re currently under the influence of cannabis. The Red Cross recommends that you avoid using marijuana on the day you’re planning to donate blood. Not only is it against the rules to give blood while in an altered state, you would also be at an increased risk of low blood pressure and lightheadedness, which could lead to fainting after giving blood.

What you need to know about donating blood and using weed

Use of cannabis doesn’t automatically disqualify you from giving blood.
The recipient of the blood will not get high – THC is quickly passed from your bloodstream into your brain and fat tissue. ¹
The Red Cross doesn’t test blood for THC.
You can’t show up for your appointment visibly impaired, under the influence of cannabis, alcohol, or any other substance.

Does the consumption method matter?

While you can give blood if you consume cannabis, you should be aware of how long the THC lasts in your system. A smoking high usually lasts a few hours, with residual effects lasting up to 6 hours. An edible high lasts for about 6-8 hours and residual effects can last over 12 hours.

That’s why it’s best to abstain from cannabis consumption on the day of your appointment.

Difference between CBD and THC in your system

The main disqualifier for giving blood if you use cannabis is showing up to your appointment visibly impaired. If you’ve recently consumed a large amount of THC and are clearly stoned for your donation, you could be asked to reschedule. CBD however, doesn’t impair cognition in the same way and the effects aren’t generally noticeable. In other words, you can use CBD and still give blood.

Who can donate blood?

Nearly anyone can donate blood! The Red Cross, the oldest blood bank in the world, has a short list of requirements for donating blood:

At least 17 years old (in most states, in the US)
In good health and feeling well
Weigh at least 110 pounds (50kg)

You cannot donate blood if you:

Have had a piercing or tattoo within the last 3 months
Are pregnant or postpartum (6 weeks after birth, according to the Red Cross)
Are a man who had sex with a man in the previous 3 months
Take medication that interferes with blood clotting
Take certain medication that can be detrimental to a growing fetus (teratogens)
Have traveled to a malaria risk country within 3 years

And while being a weed smoker doesn’t preclude you from donating blood, you may be restricted from donating blood or plasma if you’ve used synthetic marijuana, also known as K2 or spice, but this guideline varies by location.

Can you smoke weed after donating blood or plasma?

Yes, you can smoke weed after donating blood. But since you have less blood (and plasma protein) in your body, there’s less for the THC to bind to, which may lead to you feeling higher than normal. When you smoke, THC is absorbed rapidly through the lungs into the bloodstream, where it is transported by plasma proteins around the body and into the brain. Less circulating plasma after donation means less protein to bind up THC, and therefore more pronounced effects. ² ³

Smoking cannabis (specifically THC) can also cause rapid heart rate and changes in blood pressure. Considering these side effects, THC could add to the risk of fainting or falling after blood donation. ⁴

Why donating blood is so important

Donating blood or plasma is a quick, nearly painless process that saves millions of lives per year. Thankfully cannabis use is not a barrier to blood donation, allowing millions of generous stoners to donate the gift of life all around the world.

Patients suffering from life-threatening conditions and those undergoing surgeries rely on the generosity of blood donors. If you are interested in donating blood, learn more here for the US and here for the UK. ⁵

Sources

Calapai F, Cardia L, Sorbara EE, et al. Cannabinoids, Blood-Brain Barrier, and Brain Disposition. Pharmaceutics. 2020;12(3):265. Published 2020 Mar 15. doi:10.3390/pharmaceutics12030265
Mathew J, Sankar P, Varacallo M. Physiology, Blood Plasma. [Updated 2021 Apr 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK531504/
Huestis MA. Human cannabinoid pharmacokinetics. Chem Biodivers. 2007;4(8):1770-1804. doi:10.1002/cbdv.200790152
Wieling W, France CR, van Dijk N, Kamel H, Thijs RD, Tomasulo P. Physiologic strategies to prevent fainting responses during or after whole blood donation. Transfusion. 2011;51(12):2727-2738. doi:10.1111/j.1537-2995.2011.03202.x
Towards 100% Voluntary Blood Donation: A Global Framework for Action. Geneva: World Health Organization; 2010. 2, Voluntary blood donation: foundation of a safe and sufficient blood supply. Available from: https://www.ncbi.nlm.nih.gov/books/NBK305666/