Does smoking cannabis prevent blood donation?

In France alone, one million patients are treated each year thanks to blood collection. Quick and painless, these gifts are essential, but still sufficiently numerous to fully satisfy medical needs at certain times.

Donating blood is therefore an extremely useful act. Still it is necessary to be able to do it without any risk for the recipients. Can you donate blood when using cannabis? (marijuana as CBD legal cannabis)? This is our question of the day.

Can you donate blood if you smoke cannabis?

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Contrary to popular belief, smoking cannabis does not prevent blood donation

In France, smoking cannabis remains illegal. Marijuana is indeed considered a narcotic and considered a drug by law, along with stronger substances like cocaine. However, the effects and risks are obviously not comparable. With regard to blood donation, smoking cannabis is not a good enough reason not to be able to donate blood.

Concretely, it is simply asked to do not consume within 48 hours prior to donation in order to minimize the presence of THC in the blood. It is indeed more the mode of consumption that can pose a problem for the recipient than the substance itself.

Thus, while intravenous drug use is absolutely prohibited for a donor, occasional smoking does not no major risk. The questionnaire prior to donation does not mention cannabis.

The interview with the doctor should, however, raise the subject of drugs. In the event of occasional consumption, and without any other contraindication, he accepts most of the time to take the donor's blood. He may, however, reserve the right to refuse collection in case of doubt on the date of last consumption or if he considers that the person does not have a clear mind.

Blood donation and CBD cannabis: is it compatible?

Yes, without a doubt ! Donating blood while consuming cannabis is, with certain precautions, entirely possible. Moreover, the risks mentioned are systematically linked to two elements: the method of taking and the presence of THC.

Le CBD is itself a molecule legal, without psychoactive effect or risk of addiction. It therefore does not present the risks of its cousin the THC. Also, CBD is not meant to be smoked. It is consumed in drops (CBD oil), in infusion (hemp herbal teas, CBD flowers, CBD resins) or in the kitchen. Here again, no risk for the person receiving the blood of a cannabidiol user.

And elsewhere

  • Belgium: in Belgium, cannabis is listed as a soft drug. It means he is possible to donate blood when you are a consumer, unless the person is under the influence at the time of the donation.
  • Canada: in Canada, cannabis is legal, including for recreational purposes. Blood donation for those who smoke marijuana is perfectly permitted. Donors are simply asked to wait 12 hours after effects end.

Did you know: contraindications to blood donation

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A recent piercing is more likely to prevent you from donating blood than a joint

Cannabis consumption is far from the only element that can prevent blood donation! Some are obvious, others are surprising or even shocking, as the reason justifying the decision is debatable.

So, to donate blood, you have to be oldat least 18 years old, but of under 70 years of age. It is also necessary weigh at least 50 kilograms. Quite logically, it is also not possible to donate blood when you are sick (positive for covid, infection and/or fever above 38°C during the two weeks preceding the sample).

More surprising, after a tattoo or piercing (classic earrings included), it is not possible to donate blood for 4 months. Just after a dental operation, there is also a time limit to respect (24 hours for a cavity or scaling, 7 days for an extraction) in order to avoid the risk of the presence of bacteria in the blood.

If you are traveling, it may also be, depending on the destinations visited, that we refuse to take your blood.

Finally, having had sex with multiple partners in the last 4 months is grounds for refusing a blood donation. In France, and only since March 2022, homosexuals are also authorized to give blood no period of abstinence.

Until 2016, gay men were simply not allowed to. Between 2016 and 2019, they had to justify one year of abstinence and between 2019 and 2022, “only” 4 months. In other countries, such as Belgium, the period of one year of abstinence is still valid.

To find out if you can donate blood and where to do so, it is also very easy to self-assess yourself online on the EFS website, the organization in charge of blood transfusion in France.

What are the risks of donating blood after consuming THC?

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The blood collected is systematically tested and processed

A person who needs to receive blood has a health problem (illness, accident). It is therefore essential not to take the slightest risk, for obvious public health reasons.

This explains the rather strict rules towards donors: priority leans in favor of the patient's right to receive uncontaminated blood, and whether it is a chemical substance, a bacterium or a virus.

However, and according to Laurent-Paul Menard, spokesperson for Héma-Québec, the organization in charge of transfusions in Quebec:

“The quantities that are found in the products that are transfused are so small that it poses no risk for the recipients”.

This is all the more true since blood samples systematically undergo a series of biological tests and preparatory treatment before being used. Conclusion, if you occasionally use cannabis and want to donate blood, be honest with donation center staff : this is not a sufficient condition for not helping others!

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