The average human body has about 5 liters of blood. To visualize how much that is, picture a 2-liter soda bottle. There’s enough blood in the average human body to fill up about two and a half of those. Whether that sounds like a lot or a little, it might feel like your doctor wants all 5 liters if you’re living with lupus.

“Has anyone had their rheumatologist order 36 blood tests requiring 15 vials of blood?” asked one MyLupusTeam member. Another replied, “Yes. I looked at the phlebotomist like she was crazy. She said my doctor was just being thorough, and it was better than getting stuck twice.”

In this article, learn why you might need so many blood tests for lupus, how much blood can be safely drawn at once, and how to make future blood collections less stressful.

Blood Tests for Lupus

Your blood can reveal a lot about what’s going on inside your body. Healthcare professionals use a needle to obtain blood samples from a vein — a process called venipuncture — to measure levels of glucose (blood sugar), electrolytes, hemoglobin, potassium, and more.

Here are a few blood tests your doctor might order to diagnose or treat lupus:

• Complete blood count (CBC) — Measures red blood cells, white blood cells, platelets, serum, and hemoglobin, a protein in red blood cells
• Antinuclear antibody test (ANA) — Checks for antinuclear antibodies, which are often elevated in people with autoimmune diseases like lupus
• Erythrocyte sedimentation rate — Detects inflammation and helps confirm a lupus diagnosis
• Antiphospholipid antibody test — Helps find out if you’re at risk for blood clots
• Creatinine test — Checks how well your kidneys are working
• Blood urea nitrogen — Checks how well your kidneys are working and can also show liver problems
• Fasting lipid profile — Measures cholesterol and helps assess heart disease risk, which is more common in people with lupus

This list doesn’t include every test. Your care team may order more blood tests to help diagnose lupus, track how the disease is progressing, or see how well lupus treatments are working. If you have questions about your test results or the different types of tests, talk to your healthcare provider.

What Is the Maximum Amount of Blood To Be Drawn at One Time?

Your doctor may order several tests at once to reduce the number of times you get stuck with a needle. Most healthy adults can safely have up to 550 milliliters of blood taken over an eight-week period. That’s about 37 tablespoons. For comparison, a typical blood donation is about 450 milliliters — about the amount in a standard pint glass.

However, some people may need to have less blood drawn. There are a few reasons your safe sample volume of blood might be lower than 550 milliliters:

• Your overall health — If you are at risk of anemia, have bone marrow issues, are receiving chemotherapy, or have other medical concerns, the safe amount may be lower.
• Your body weight — Over an eight-week period, the amount of blood drawn should not be more than 10.5 milliliters for every kilogram (around 2.2 pounds) of your body weight if that total is less than 550 milliliters.
• Your age — For children 12 and under, pediatric doctors recommend drawing the lowest of these three amounts: 2.4 milliliters per kilogram of body weight, 50 milliliters, or 3 percent of the child’s total blood volume.

If you are under the care of multiple healthcare professionals, make sure the one requesting blood work for lupus is aware of any treatment you are receiving, including blood clotting or thinning medications or blood transfusions, as well as health conditions you may have, such as anemia.

How Much Blood Is in a Testing Vial?

It may feel like the phlebotomist (a healthcare professional who draws blood) is taking a lot of blood at once if they fill multiple blood collection tubes. But a standard testing vial holds between 2 and 8.5 milliliters of blood — that’s about half a tablespoon or less. For routine laboratory testing, like a CBC and metabolic panel, they may only need about 10 milliliters of blood — just 2 teaspoons total.

How Many Tubes of Blood Can Be Drawn at Once?

Even if your blood fills 20 tubes that hold 8 milliliters each, that’s still only 160 milliliters — much less than a typical blood donation or the maximum safe amount. In fact, it would take about 68 8-milliliter tubes to reach 550 milliliters. But that’s very unlikely. Many tests can be done using blood from one tube, so you don’t usually need to give that much at once.

Also, most vials are not completely empty before they’re used. The colored caps on test tubes show what kind of additive is inside. These additives help prepare your blood for different types of tests. For example, some test tubes might have an anticoagulant (a substance that reduces blood clotting) like potassium EDTA or sodium fluoride, while others might have a clot-activator gel to speed up blood clotting.

Tips for Your Next Blood Draw

If you have questions about blood tubes or you’re nervous about the amount of blood your healthcare provider ordered, it’s OK to ask. And if you feel anxious as the vials fill up, take a deep breath and remember that you’re not alone. Many people with lupus have been there too.

“I used to make a game out of seeing what my high number was,” shared one MyLupusTeam member. “I think my record draw is 18 vials.” Another MyLupusTeam member said, “My highest number is 23 vials at once.”

Watching blood flow out of your body into a blood collection tube or vial can be nerve-racking for anyone. Fear of needles is so common it even has a name: trypanophobia.

Although you can’t avoid blood work if you have a chronic health condition like lupus, there are a few steps you can take to make it easier. Here are a few tips for better blood draws:

• Let the person drawing blood know if you’re nervous.
• Look away while they insert the needle.
• Practice deep breathing or meditation.
• Distract yourself by talking to someone or scrolling through social media.
• Bring headphones and play calming music.
• Ask a friend or family member to come with you.
• If you’ve fainted while getting blood drawn before, ask if you can lie down during the draw.
• Speak up immediately if you feel lightheaded or queasy.

If you feel anxious because the last person drawing your blood had to stick you more than once to find a vein, try drinking water before your next appointment. Being well hydrated makes your veins fuller and easier to find, which can help the nurse or technician get it right on the first try.

You can also talk to your healthcare provider if blood draws are very stressful for you. If your anxiety is strong, they may prescribe medication, refer you to a therapist, or offer additional coping solutions to make blood draws easier. Speak up and ask for the support you need.

Talk With Others Who Understand

MyLupusTeam is the social network for people with lupus and their loved ones. On MyLupusTeam, people come together to ask questions, give advice, and share their stories with others who understand life with lupus.

Do you have any tips for blood draws? Share your experience in the comments below, or start a conversation on your Activities page.