In most places, you can donate blood 12 hours after using marijuana.
Since marijuana can be detected in your blood several days after consumption, some people believe that users can’t donate blood.
However, this is not true. Cannabis users can still participate in blood drives as long as other factors do not disqualify them.
If you want to use marijuana the day of your blood donation, it’s best to wait until a few hours after to prevent lightheadedness or fainting.
Can Marijuana Users Donate Blood?
Marijuana users can donate blood as long as they’ve been sober for at least 12 hours. The high will not be passed on to the blood transfusion recipient.
When you consume marijuana, the active ingredient THC enters the brain, creating the intoxicating effects. Over the next few hours, your body then metabolizes THC into THC-COOH.
After this process is finished, your body contains only the chemical THC-COOH — which is non-psychoactive. This means that you are no longer high and the transfusion recipient won’t experience any effects.
If you show up to a blood donation clinic high, your body isn’t finished metabolizing the THC and you’ll likely be rejected. This is why clinics require you to be sober for several hours beforehand.
In addition, donors need to reliably answer a questionnaire and consent to a blood draw. This cannot happen if you’re under the influence of any drugs or alcohol.
If you want to use cannabis the day of your blood donation, it’s best to wait until a few hours after the appointment.
Since marijuana and drawing blood both lower blood pressure, using immediately afterward is not recommended. The combination of the two may lead to lightheadedness or fainting.
What Do Guidelines Say?
Guidelines for most, if not all, American and Canadian blood clinics state that donors can be accepted if they use cannabis.
Although the American Red Cross says it “does not encourage the use of controlled substances,” marijuana use will not automatically disqualify you from giving blood.
The organization says “as long as you are feeling well” (meaning you don’t arrive high), you can donate.
Similarly, the New York Blood Center—which takes in 2,000 donors daily—accepts pefzple who use marijuana as long as they’re not under the influence.
Canadian Blood Services allows marijuana users to donate as long as they’ve been sober for at least 12 hours. Some clinics may ask about your cannabis use to determine if you’re sober, although your answers remain confidential.
In Europe, guidelines for donating blood vary. In some countries such as Norway, cannabis users cannot donate because it’s believed that their blood is contaminated. If a user wishes to donate, they must abstain from the drug for at least a year before the donation.
If you’re a regular marijuana user, the drug can be detected in your blood up to seven days after your last consumption. However, the American Red Cross and Canadian Blood Services do not screen donations for cannabis. The clinic won’t know you’re a cannabis user unless you tell a nurse during your questionnaire.
Common Reasons You Can’t Donate Blood
Before donating blood, a mini-physical and questionnaire will determine if you’re eligible. Although marijuana use doesn’t prevent you from donating blood, other factors may disqualify you. You may not be eligible if you:
- Are under age 17
- Don’t meet the height and weight requirements
- Have an acute infection or certain diseases
- Have abnormal blood pressure
- Have had risky sex including unprotected sex
- Have recently given birth or are pregnant
- Have travelled to certain countries
- Have ever used intravenous illegal drugs
- Have gotten a tattoo or body piercing in an unlicensed facility or with unsterile needles
- Have had a tattoo or body piercing in the last six months, even in a licensed facility
- Are putting your own safety or health at risk by donating
While using medical marijuana itself won’t disqualify you, the condition you’re using it for may. For example, people with cancer or Crohn’s disease may be rejected.
If you plan on helping the cause, clinics recommend that you get a good night’s sleep, eat a balanced meal, drink plenty of water and show up sober.