Jul 23, 2023

How to prepare for a blood test and make it easier

Q: I hate getting my blood drawn. It’s always hard to find my veins. Are there any ways to make it less awful?

A: Needles can hurt and having to be poked multiple times to find the vein is a special form of torture.

Hydrating the day before a blood draw and keeping your arms warm as you head into the lab can make for a smoother experience. Staying calm is also important, though that’s easier said than done. Priming your nerves — and your veins — can help make a difference.

Hydrate in advance: Experts usually recommend to start hydrating the day before you know you’ll go in. The goal isn’t to drink excessively, but to ensure you’re not dehydrated, which can decrease blood volume. Water is generally allowed even when the bloodwork is supposed to be done “fasting,” but make sure to check with your medical provider beforehand.

Warm up your arms: Wearing long sleeves that you can roll up is a good idea, but I suggest going a step further: Bring some hand warmers and rub them up and down your arms to dilate the veins before the stick. You can also try running your forearms under warm water in a bathroom or ask if the lab has a hot towel you wrap around them.

Speak up about your veins: Certain people, especially those who are elderly or chronically ill, have “rolling veins” — meaning the collagen in tissues that anchor veins in place are weakened, causing the vessels to “roll” when approached by a needle. Tell the technician if that sounds like you. Some facilities might have technicians who are more accustomed to patients with difficult-to-find veins or use tools like vein finders or ultrasounds that can help identify a good vessel. If the technician got a needle in easily, ask them which vein they used so you’ll know for the future.

There is nothing worse than undergoing a needle-stick only to discover the sample “hemolyzed,” meaning the blood cells burst, rendering testing inaccurate. It often happens because of how the tube is handled after the blood is drawn, but sticking a larger vein — like from the antecubital fossa in the crook of your elbow — has been shown to reduce the risk of hemolysis, while having the tourniquet on for longer than a minute raises those odds.

Calm yourself with a breathing exercise: Make sure you aren’t holding your breath. Instead, take deep breaths rising from your stomach, rather than your chest. If that’s not for you, try distracting yourself by scrolling through TikTok or chatting with the technician. Some people deliberately pinch the opposite side of the body to distract their brains while the needle goes in, but if this will only stress you out further, I wouldn’t advise it.

Press on the bandage: To prevent bruising, hold pressure over the dressing for a few minutes — not seconds — after the technician is done. Avoid carrying anything very heavy with that arm for an hour or two afterward.

Don’t hesitate to speak up if you’re feeling very nervous or faint before, during or after a blood test. Be sure to inform the technician if you’ve fainted due to bloodwork in the past. They may go straight to using a butterfly needle, which is thinner than the standard variety and tends to hurt less (though it’ll take longer to get your blood drawn). They can also bring in backup or have you recline during the needle-stick to protect you from grabbing some floor.

So why does this happen? Fainting at the sight of blood is thought to be caused by the vagus nerve, which is responsible for calming the body and aiding in digestion. When it goes overboard, your heart rate and blood pressure plummet and your brain’s blood supply dips, leading to blurry vision, lightheadedness and loss of consciousness.

Various theories have been proposed about how this reaction could have been evolutionarily beneficial: When struck by a predator, fainting can make you appear dead, shielding you from further attack. And if you sustain an injury from a sharp object, a drop in blood pressure and heart rate might mitigate the blood loss. My own theory is that fainting is self-protective against pain. If you’ve been mortally wounded, losing consciousness would make those last moments less distressing.

Physical maneuvers — such as crossing your legs and clenching your glute muscles — have been shown to rapidly combat fainting tendencies during blood draws. Just be careful not to bear down like you would during a bowel movement as this can actually impede blood return to the heart. People with an extreme fear of blood or the related blood-injury-injection phobia may benefit from cognitive behavioral therapy.

Not every blood test I order is urgent. If you have multiple physician visits in a month, don’t be shy to ask your doctor if it’s safe to wait to get your blood drawn in one batch after all your appointments are completed. If it’ll spare you an extra needle-stick, waiting another week or two is often completely fine, but so many people never ask.

Meet the doctor: Trisha S. Pasricha is a physician at Massachusetts General Hospital, an instructor in medicine at Harvard Medical School and a medical journalist.

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