What Is a Hemoglobin Test?

What to expect when undergoing this test

In This Article

A hemoglobin test measures the amount of hemoglobin (Hb or Hgb) in your blood. This protein in your red blood cells (RBCs) carries oxygen and carbon dioxide between the lungs and the rest of the body. An altered hemoglobin level is often a sign of disease. Without the right amount, your body may not have enough energy to function optimally.

A blood test that measures hemoglobin is part of a routine check-up. Your doctors might also order a hemoglobin test for you if they are concerned about your health.

Risks of High and Low Hemoglobin Levels
Verywell / JR Bee

Purpose of Test

A hemoglobin level is part of a standard complete blood count (CBC), so you may have your level measured when you have your routine yearly physical—even if you don't have symptoms. A hemoglobin test is also part of the standard comprehensive newborn screening.

But there are times when doctors may order this test for a more specific reason.

If you have symptoms consistent with altered hemoglobin, you may have this test to help determine the cause of your symptoms. These may include:

  • Fatigue, low energy
  • Dizziness
  • Generalized weakness
  • Weight loss or malnutrition
  • Jaundice (yellow skin and/or eyes)
  • Blood in the urine or stool
  • Bruising
  • Severe trauma
  • Excessive vomiting

You may also periodically need this test to monitor a known medical illness that affects your hemoglobin.

Risks and Contraindications

You will have your blood collected for your hemoglobin test.

There very few risks to this procedure. If you've had a reaction when having a blood test before, you can expect the same with this test (e.g., puncture site soreness). If you tend to get squeamish around blood or needles, you may feel dizzy or lightheaded.

While it's rare, there is a slight risk of infection, especially if the area of needle insertion becomes exposed or gets dirty before the skin heals.

Bleeding

You may have some bruising or swelling around the area where the needle is inserted, especially if you have a bleeding disorder like hemophilia or if you take a blood thinner such as aspirin or Coumadin (warfarin).

Before having your blood collected, let the nurse or phlebotomist who is drawing your blood know if you have these risk factors. You may need a pressure bandage afterward to stop the bleeding and/or they may ask you to stay until they have confirmed that your bleeding has stopped.

Before the Test

You don't need to do anything in advance to prepare for your hemoglobin level test.

It's unlikely that your doctor will tell you to stop taking your blood thinner, especially if you take it to prevent a heart attack or stroke. But you may be advised to avoid using nonsteroidal anti-inflammatories (NSAIDs) for pain relief the day before your test if you have a bleeding tendency.

Timing

The process of taking a sample of your blood normally takes less than five minutes. However, you need to allot at least an hour for the test.

You will have to register, wait your turn, and wait for the phlebotomist to make sure that your puncture site is not bleeding before you can leave.

Location

You might have your test done in your doctor's office, a phlebotomy lab (on-site or off-site), or at the hospital.

What to Wear

You don't need to wear anything special for a hemoglobin test. Avoid tight shirt sleeves since you'll need to roll up your sleeve to have your blood collected.

Food and Drink

If you are just getting a hemoglobin test, you don't need to make any adjustments in your diet ahead of time.

If you are also going to be having other blood tests at the same time (such as blood glucose), then your doctor may advise you to fast for around eight hours before the test.

Cost and Health Insurance

Generally, the cost of a hemoglobin test or a CBC is covered (partially or in full) by insurance and Medicare or Medicaid. If you aren't sure if your test will be covered, you can contact your health insurer or the location/lab where you will have your test done to confirm. Check if you will be required to pay a co-pay or a deductible.

If you are paying for your test out of pocket, you can expect the cost of a hemoglobin test to range between $5 to $30, and the cost of a CBC to range between $10 and $35.

What to Bring

Make sure you bring a form of identification, your insurance information, and a form of payment in case you are paying the whole cost of your test or some of the cost.

During the Test

Your blood will be drawn by a nurse or a phlebotomist. The sample is then sent to a lab for processing.

Pre-Test

You may need to fill out forms when you check-in for your test to authorize billing and to release your test results to your physician(s).

Throughout the Test

Your nurse or phlebotomist will ask you to sit down and choose the arm you'd prefer to use. (Many choose their non-dominant arm in case soreness results.) They will find a vein from which to collect blood, possibly inside the crease of your elbow.

You will have a tourniquet tied above the vein. After the area is cleaned, a small needle will be inserted into your vein and your blood will be collected in a tube. You may feel a small poke, possibly with mild discomfort and/or pain.

If you have a tendency to feel lightheaded or dizzy around needles or blood, it's helpful to look away during the procedure. Tell your nurse if you feel like you're going to faint and/or if you have fainted before during a similar procedure.

Your nurse or phlebotomist will take off the tourniquet before removing the needle from your arm. Then they will press gauze over the puncture site to stop bleeding and apply a bandage.

Finger-Prick Alternative

If your baby is the one having this test, usually their heel will be pricked for a blood sample. There are also finger-prick tests available for measuring hemoglobin in adults. These tests are used in certain circumstances, such as when a nearby lab isn't available or when you are having a pre-test before donating blood.

If you're having a finger prick, your finder tip will be cleansed and quickly pricked with a tiny needle. You may feel a sharp poke, but it only lasts for a second.

Post-Test

If you feel fine, you'll be free to go as long as the bleeding has stopped. If you are lightheaded or dizzy, you may need a little time to recover before you can leave.

After the Test

Once you're done with the test, you can go about your normal activities. On the first day after your blood is collected, it's a good idea to avoid lifting very heavy items with the arm that was used for your blood collection.

If your arm is sore, you should take it easy and you can place an ice pack on it.

Managing Side Effects

You may experience some bruising, swelling, or slight pain in the area the needle was, but this should be minor and last no more than a few days. If it persists or is getting worse, call your doctor.

Also call your doctor if you develop a fever or if the area where blood was drawn becomes warm, very painful or swollen, or oozes blood or pus.

Interpreting Results

If a finger-prick test was performed, the blood may be placed in a digital machine that provides results within minutes of the sample being drawn. Results of a typical blood draw for a hemoglobin test will be ready within a day or two.

Your doctor will consider your medical history, physical examination, and other diagnostic tests when interpreting your hemoglobin test results.

In most cases, your doctor will interpret the results of your hemoglobin level test along with results of other blood tests. If your hemoglobin is being measured as part of a CBC, your RBC count and hematocrit level will be available as well.

Sample Hemoglobin Level Reference Ranges
For Approximate Range
Women 12.0 to 15.5 gm/dl
Men 13.5 to 17.5 gm/dl
Children 11 to 16 g/dl
Pregnant Women 11 to 12 g/dl
Consult your lab or physician for appropriate reference ranges for your results.

Low Hemoglobin

Low hemoglobin levels may be reflective of the body's reduced production of hemoglobin, decreased production of RBCs, or the destruction or loss of RBCs.

Low hemoglobin levels are associated with:

Diseases like sickle cell disease, thalassemia, and glucose-6 phosphate dehydrogenase (G6PD) deficiency may cause low hemoglobin levels when RBCs become severely low during a crisis.

Your hemoglobin level may also be low after you donate blood. In this case, you should expect it to normalize after a few weeks.

High Hemoglobin

Elevated hemoglobin levels can mean that the body is making too many RBCs or that the body is low in fluid volume, such as with dehydration.

Keep in mind that elevated hemoglobin, even when it is the result of the body compensating for disease (such as lung or heart disease), is a sign of poor health.

Elevated hemoglobin levels are associated with:

  • Polycythemia vera, a rare condition that causes your bone marrow to produce too many red blood cells
  • Smoking
  • Kidney cancer
  • Chronic lung disease
  • Heart failure
  • Living at high altitude
  • Dehydration

Follow-Up

You may need additional testing and/or treatment if you have an abnormal hemoglobin level.

For instance, if your doctor is concerned about a bleeding ulcer or kidney disease, you may need additional tests to identify the cause of your altered hemoglobin level.

And if your low hemoglobin is caused by iron deficiency due to inflammatory bowel disease (IBD), treatment for both issues can help restore your hemoglobin to a normal level.

A Word From Verywell

Hemoglobin levels are a helpful indicator of a number of medical issues. Since you are unlikely to have a hemoglobin level without other blood tests too, an assessment of the combination of test results will be helpful as your medical team evaluates your overall health.

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