Can You Donate Blood If You Smoke Weed?

One of the most asked questions we get on social media is, can you donate blood if you smoke weed? According to the available information, smoking cannabis shouldn’t prevent you from donating blood. However, if you’re visibly high when you show up to the clinic, your donation may not be welcome! Read on to find out more…

Can You Donate Blood If You Smoke Weed? – What Do We Know?

Well, if you’ve read our recent article How Long Do Cannabis Metabolites Stay In Your System?, you’ll know that THC only remains in the blood for around 12-24 hours after occasional use, and for around 2-7 days for heavier, more regular users of cannabis. So, if you really want to be sure that you don’t have any traces of THC in you blood when you donate, you can take a 7-day T-break and give blood at the end of it.

But if you don’t take that T-break, can you (and should you) still give blood? Let’s take a look at what existing guidelines state in key locations around the world. In the UK, guidelines state that you must not give blood or platelets if: “You have ever injected, or been injected with, drugs; even a long time ago or only once. This includes body-building drugs and injectable tanning agents”.

In the USA, the American Red Cross states that: “Those who have ever used IV drugs that were not prescribed by a physician are not eligible to donate. This requirement is related to concerns about hepatitis and HIV”.

The Australian Red Cross states: “Maybe. It depends on the type of drug and how and when it was taken. If you have ever injected drugs not prescribed by a registered medical practitioner, even once, you’re not eligible to donate”.

As we see, there is no specific mention of cannabis use as a bar to donation. Furthermore, the reason that intravenous drug use is a bar to donation is more to do with the risk of infections being transferred than any inherent risk arising from the intravenous drugs themselves.

So – in the USA & UK, as long as you’re not injecting your THC (please don’t do that…), you’re good to go! In Australia, although the wording is a little more ambiguous, it’s unlikely that cannabis use would be seen as a bar. However, it may be a different story if you’re under the influence of cannabis when you arrive.

What If I Turn Up High To The Clinic?

So if you’re a regular cannabis user, there’s no particular reason that you can’t donate blood. However, what could happen if you are deemed to be high at the time you show up to the clinic?

Well, in Australia at least, they may for sure decline your offer to donate. They are ambiguous on whether recreational drug use in general in a bar to donation and they also specify: “We do not take blood from anyone under the influence of alcohol. This is because being intoxicated can affect your ability to understand and answer the donor questionnaire and declaration”. On this basis, they could argue that you didn’t have the capacity to make decisions if you were visibly high when you appeared.

The American Red Cross “does not encourage the use of controlled substances, (but) marijuana or alcohol use does not necessarily disqualify you from giving blood as long as you are feeling well”. So if you’re visibly high, you may be deemed “unwell” by clinic staff.

Furthermore, Bloodworks Northwest, another major US blood bank, states: “We cannot accept blood from anyone who is intoxicated with alcohol, cannabis, or prescription drugs because of the possibility of an unreliable history and the inability to give consent for the draw“. But they go on to state that THC testing is not required.

The UK doesn’t state anything specific about intoxication. They recommend you don’t drink alcohol: “It is essential to avoid alcohol before and after donating as this may affect hydration levels and delay recovery” – but that seems to be more of a health concern than anything else.

So for the most part, unless you are very obviously high, you’d probably be able to donate blood while under the influence of cannabis. But is that the best idea anyway? Maybe not.

Cannabis & Hypotension

Cannabis use can occasionally lead to the dreaded phenomenon known as the “white-out”, which involves dizziness, shakiness, pale skin, loss of balance, and even fainting. It’s usually temporary and is not dangerous in itself, but the loss of balance can cause injuries if the individual falls over, for example. Furthermore, it’s an unpleasant and worrying experience.

So what connection does this have with blood donation? Well, a “white-out” occurs due to a rapid drop in blood pressure, particularly when standing up from a sitting or lying position. This is known as “orthostatic hypotension”.

Another thing that causes a drop in blood pressure is, you’ve guessed it – donating blood. Sometimes, the process of giving blood causes effects very similar to a white-out: dizziness, faintness, loss of balance and so on.

So, while there’s no direct evidence of cannabis use adding to this effect, it certainly seems to be a possibility. That shouldn’t put you off from giving blood, but it may be advisable to hold off on cannabis use for a few hours before and after donating, to avoid the possibility of ill effects.

If you do feel faint after giving blood, whether you’ve used cannabis or not, the best thing to do is drink plenty of fluids and eat salty snacks. If you have used cannabis, sugary snacks may also help, as orthostatic hypotension and cannabis use may also be linked with low blood sugar.

What do the guidelines on giving blood say about cannabis in your country? Let us know in the comments!