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Patient education: Homocysteine blood test (The Basics)

Patient education: Homocysteine blood test (The Basics)

What is a homocysteine blood test? — 

This measures the amount of homocysteine in the blood. Homocysteine is an "amino acid," which is a building block of protein. Normally, the body uses certain B vitamins to break down homocysteine. This creates other substances the body needs.

Why might I get a homocysteine blood test? — 

Your doctor might order this test:

●If they think you might have a condition called "homocystinuria"

●To help diagnose low levels of certain B vitamins, like vitamin B12 and folate

How do I prepare for a homocysteine blood test? — 

You need to get a "blood draw." Your doctor or nurse will tell you where to go for this.

It might help to wear a short-sleeve shirt to your blood draw appointment. This makes it easier for the person drawing your blood to get to your arm.

What happens during a blood draw? — 

A needle is used to take a small amount of blood from your arm (figure 1). Collecting the blood only takes a few minutes. The blood is then tested in a lab.

Tell the person who takes your blood:

●If you take "blood thinner" medicines or have a bleeding problem – They will make sure your bleeding is under control before you leave.

●If you have a latex allergy – Some of the supplies used for blood draws might contain latex.

●If you have a preferred arm to use

Most of the time, getting blood taken does not cause problems. You might have a little soreness or bruising where the needle went in.

What do my results mean? — 

Your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.

If your homocysteine blood test shows any abnormal results, your doctor or nurse will talk to you about what to do next. They might need to do more tests to figure out the cause.

If you do have a health problem, your doctor will work with you to come up with a treatment plan.

More on this topic

Patient education: Vitamin B12 and folate blood test (The Basics)
Patient education: Vitamin B12 deficiency and folate deficiency (The Basics)

This topic retrieved from UpToDate on: May 11, 2025.
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