Huge blood test myth has finally been busted
Welcome to Ask Doctor Zac, a weekly column from news.com.au. This week, Dr Zac Turner explores whether or not blood tests are back for you.
QUESTION: Dear Dr Zac, I saw a doctor on Instagram saying that getting blood tests can make you more sick, because the more blood you have drawn, it's taking away your immune system? Is that true or just social media pseudoscience? – Amanda, 27, Gold Coast
ANSWER: If I had a dollar for every time an 'Instagram doctor' spread weird health advice, I'd be rich enough to launch my own line of overpriced supplements and film it shirtless in a rainforest.
Let's get straight to it: The claim that drawing blood somehow removes your immune system is complete nonsense. According to this so-called 'Medical Medium' (who, by the way, says his info comes from a spirit – yes, really), taking blood for tests will make you sicker because it weakens your immune system. That's not just wrong, it's dangerously misleading.
Here's why you shouldn't panic if your GP orders a blood test – and why listening to ghost-guided wellness influencers could do more harm than a few millilitres of blood ever could.
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Blood tests don't drain your immune system – just your TikTok feed.
Let's bust the myth first: Your immune system doesn't live in your blood like it's floating around in a tiny lifeboat. Yes, some immune cells are in your bloodstream, but they're constantly being produced by your bone marrow and lymphatic system. Drawing a small amount of blood doesn't cripple your defences, it gives your doctor valuable clues to help strengthen them.
Standard blood tests typically take about 5–10ml of blood. That's around two teaspoons. The average adult has five litres of blood. You've probably lost more than squeezing a pimple or stubbing your toe in the dark.
Even if you get extensive testing done, say 50ml worth, it's still less than 2 per cent of your total blood volume. Your body replenishes that quickly, usually within 24–48 hours. Unless you're a lizard person (or actively haemorrhaging), you'll be just fine.
But what about people who feel worse after blood tests?
This is where things get a bit nuanced. Some people do feel faint, dizzy or tired after having blood drawn. But that's more to do with how the blood was taken (and whether you had breakfast) than the blood itself.
Feeling queasy is often linked to: Vasovagal response (a fancy way of saying your body freaks out at needles), Low blood sugar, or anxiety.
These are temporary reactions, not signs your immune system is crumbling.
Where did this bizarre idea come from?
The quote in question comes from Anthony William, aka the 'Medical Medium'. He claims to hear health advice from a spirit (who apparently skipped immunology class).
Is a blood test dangerous? Picture: iStock
He's not a licensed doctor, has no formal medical training, and has previously claimed celery juice can cure everything from anxiety to shingles. He's also built a multimillion-dollar wellness empire promoting unproven health advice, often to people who are desperate and vulnerable. That, in my opinion, is the real sickness.
Sure, he throws in the odd disclaimer like 'work with your doctor,' but that's like a car salesman saying 'test the brakes' while handing you a steering wheel held on with duct tape.
Here's what you actually should do around blood tests
If you're sick or dealing with chronic illness, your doctor might want to order blood work to understand what's going on. That's a good thing. The faster you get the right diagnosis, the faster you can get the right treatment.
Some basic tips for a smooth blood test experience:
• Drink plenty of water beforehand (it makes veins easier to find)
• Don't skip meals unless told to fast
• If you get dizzy, let the phlebotomist know, they can take extra care
• Rest afterwards if needed, and have a snack
Unless you've been told to fast, don't skip meals. Picture: iStock
That's it. No sage burning or spirit communication required.
The only thing scary about blood tests is the fact that some influencers think they're dangerous. Removing 5ml of blood won't wreck your immune system – but believing Instagram pseudoscience just might.
Blood tests are safe, essential, and can literally save your life. And if someone tells you otherwise while claiming to get their health info from ghosts, maybe it's time to unfollow.
You've got this.
Dr Zac
Got a question? Email askdrzac@conciergedoctors.com.au
Follow @DrZacTurner on Instagram
Dr Zac Turner is a medical practitioner specialising in preventative health and wellness. He has four health/medical degrees – Bachelor of Medicine/Bachelor of Surgery at the University of Sydney, Bachelor of Nursing at Central Queensland University, and Bachelor of Biomedical Science at the University of the Sunshine Coast. He is a registrar for the Australian College of Rural and Remote Medicine, and is completing a PhD in Biomedical Engineering (UNSW). Dr Zac is the medical director for his own holistic wellness medical clinics throughout Australia, Concierge Doctors.
Originally published as Huge blood test myth has finally been busted
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