What Is a Hemoglobin Test?

Hemoglobin (HEE-muh-glow-bin), or Hb, is a protein inside red blood cells that carries oxygen. A hemoglobin blood test helps doctors check the level of this protein. Knowing this amount reveals how well the blood can carry oxygen to the different parts of the body.

Why Are Hemoglobin Tests Done?

Doctors will order a hemoglobin test to check the health of your child’s red blood cells. It’s done as part of a test called a complete blood count (CBC), which also tells how many red blood cells, white blood cells, and platelets the blood has. Doctors might do a CBC as part of a routine checkup to screen for problems or because a child isn't feeling well.

Top Things to Know

• A hemoglobin test checks the health of red blood cells in the body.
• Doctors might order the test as part of a checkup or to see why a child feels sick.
• Kids may need to stop taking certain medicines and avoid extreme exercise before the blood test.
• Your doctor can explain what it means if hemoglobin levels are low or high.

How Can I Help My Child Prepare for a Blood Test?

Tell your doctor if your child is taking any medicine or has recently exercised a lot. These things may change the level of hemoglobin.

To help kids get ready for a blood test, find out if they need to fast (not eat or drink) or should stop taking medicines before the test. Explain what to expect during the test. If your child is nervous about it, work together on ways to stay calm. Deep breathing or even imagining being in a place that makes your child feel safe and relaxed can help.

What Do Hemoglobin Blood Test Results Mean?

Your doctor will explain what the results of the hemoglobin test mean for your child. What’s “normal” can vary based on things like age and sex.

Low Hemoglobin Level

If the hemoglobin level is low, oxygen can’t be delivered as well to the body’s organs and tissues. The level might be lower than usual due to things like:

• problems with red blood cells (such as anemia), bone marrow, or kidneys
• poor nutrition or not eating enough of vitamins B6 or B12, folate, and iron
• more water in the body than usual
• pregnancy

High Hemoglobin Level

High hemoglobin levels can cause blood to thicken and be sluggish, and can lead to symptoms like headaches or blood clots. Hemoglobin levels are often high when there’s been too little oxygen in the blood for a long time. This might be due to things like:

• dehydration
• problems with red blood cells (such as polycythemia), bone marrow, heart, lungs, or kidneys
• smoking
• high altitude

What Else Should I Know?

If you have questions about hemoglobin testing or what the results mean, talk with your doctor.