Do you feel woozy when having blood drawn?
Feet tingling, vision greying and the room spinning are classic warning signs some people feel during a blood draw just seconds before they faint.
About 2% to 5% of people lose consciousness during or immediately after having their blood drawn. This typically occurs due to the sudden drop in their heart rate and blood pressure triggered by pain, the sight of blood or heightened anxiety.
Dehydration, fasting too long and standing up quickly after the blood draw all increase your risk since they can lower blood volume and blood pressure. People with needle phobia – which affects at least one in 10 adults – are particularly vulnerable.
“When your brain interprets the needle as a danger, it flips a switch that diverts blood away from the head,” says Dr. Elizabeth Joseph, an internal medicine physician at Aurora Health Care. “That protective reflex is meant to keep you safe, but it also makes you woozy and can knock you out for a moment.”
Dr. Joseph offers the following tips on how to avoid passing out during a blood draw:
- Drink plenty of water. Aim for two to three extra glasses of water the evening before and the morning of your test. Adequate fluid levels raise circulating blood volume and make veins easier to see.
- Eat a light meal unless you have to fast: Low blood sugar can worsen dizziness. If fasting is required, ask if you can still drink plain water.
- Dress in layers: Warmth dilates blood vessels, easing the stick and reducing discomfort.
- Tell the staff your fainting history: They can take your blood while you lie flat or with your legs elevated, which prevents the sudden pressure drop.
- Look the other way: Looking away during a blood draw is a helpful technique because it can reduce anxiety and prevent reactions like fainting or lightheadedness.
When having your blood taken, use controlled breathing or guided imagery to lower your anxiety. Counting backward from 100 or talking with the phlebotomist keeps the brain occupied.
If you start feeling clammy, speak up immediately. Lying back, elevating your feet or placing a cool cloth on your forehead allows blood to return quickly to the brain and usually reverses symptoms within seconds.
Remain seated for several minutes, sip water and avoid sudden movements. If multiple vials of blood are needed, ask whether the collection can be split into two sessions on different days to shorten the visit.
Occasional fainting tied to needles is usually harmless, but frequent episodes deserve a medical workup to rule out heart rhythm problems, anemia or low blood pressure disorders, Dr. Joseph notes.
It’s important to complete blood draws as recommended by your health care provider as they give an insight into your health and can rule out and help diagnose various medical conditions.
Are you worried about your heart health? Take a free online quiz to learn your risk for heart disease.
