Skip to main content Skip to navigation

Serum Free Hemoglobin Test – Indications, Procedures, Results

Last updated: February 8, 2026 Medically reviewed by: RxHarun Orthopedic Specialist Doctor Reading time: 8 min read

Blood hemoglobin; Serum hemoglobin; Hemolytic anemia – free hemoglobin

Serum-free hemoglobin is a blood test that measures the level of free hemoglobin in the liquid part of the blood (the serum). Free hemoglobin is the hemoglobin outside of the red blood cells. Most of the hemoglobin is found inside the red blood cells, not in the serum. Hemoglobin carries oxygen in the blood.

Serum-free hemoglobin is a blood test that measures the level of free hemoglobin in the liquid part of the blood (the serum). Free hemoglobin is the hemoglobin outside of the red blood cells. Most of the hemoglobin is found inside the red blood cells, not in the serum. Hemoglobin carries oxygen in the blood.

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

No preparation is necessary.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

Hemoglobin (Hb) is the main component of red blood cells. It is a protein that carries oxygen. This test is done to diagnose or monitor how severe hemolytic anemia is. This is a disorder in which a low red blood cell count is caused by the abnormal breakdown of red blood cells.

Normal Results

Plasma or serum in someone who does not have hemolytic anemia may contain up to 5 milligrams per deciliter (mg/dL) or 0.05 grams per liter (g/L) hemoglobin.

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different samples. Talk to your health care provider about the meaning of your specific test results.

What Abnormal Results Mean

A higher-than-normal level may indicate:

  • A hemolytic anemia
  • Condition in which red blood cells break down when the body is exposed to certain drugs or the stress of infection ( G6PD deficiency )
  • Low red blood cell count due to red blood cells breaking down sooner than normal
  • Blood disorder in which red blood cells are destroyed when they go from cold to warm temperatures ( paroxysmal cold hemoglobinuria )
  • Sickle cell anemia
  • Disorder in which there is excessive breakdown of hemoglobin ( thalassemia )
  • Transfusion reaction

Risks

Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

  • Excessive bleeding
  • Fainting or feeling lightheaded
  • Hematoma (blood buildup under the skin)
  • Infection (a slight risk any time the skin is broken)

FAQ

How is the serum hemoglobin test performed?

  • For a hemoglobin test, a member of your health care team takes a sample of blood by pricking your fingertip or inserting a needle into a vein in your arm. For infants, the sample may be obtained by pricking the heel. The blood sample is sent to a lab for analysis.

What fruit is highest in iron?

  • Prune juice, olives, and mulberries are the three types of fruit with the highest iron concentration per portion. This fruit also contains antioxidants and a variety of other nutrients beneficial to health.

Which nuts are high in iron?

Today we are listing out nuts that are rich in iron. Read on to know more.
  • Cashew nuts. This particular nuts pack a good amount of iron. …
  • Peanuts. Peanuts which are commonly known as moongfalli is widely used in the Indian kitchen. …
  • Pistachios. Many people love pasta.
  • Almonds.
  • Walnuts.

What causes hemoglobin to drop?

  • Low hemoglobin is caused by: Low iron intake in the diet or low iron absorption. Menstrual bleeding. Bleeding from any cause, including surgery,3 trauma, or a gastrointestinal bleed from an ulcer.

What is a healthy hemoglobin level by age?

  • 1-6 years: 9.5-14 g/dL. 6-18 years: 10-15.5 g/dL. Adult men: 14-18 g/dL. Adult women: 12-16 g/dL.

What is a hemoglobin test looking for?

  • A hemoglobin test is often used to check for anemia, a condition in which your body has fewer red blood cells than normal. If you have anemia, the cells in your body don’t get all the oxygen they need. Hemoglobin tests are measured as part of a complete blood count (CBC).

What would happen if hemoglobin was free in plasma?

  • If the 150 g L−1 Hb were free in plasma it would raise the viscosity to intolerable values, and colloid osmotic pressure would also increase considerably.

What is free hemoglobin?

  • Free hemoglobin is the hemoglobin outside of the red blood cells. Most of the hemoglobin is found inside the red blood cells, not in the serum. Hemoglobin carries oxygen in the blood.

Which fruit is best for hemoglobin?

  • Rely on Fruits: Apricots, apples, grapes, bananas, pomegranates, and watermelons play a very important role in improving hemoglobin count. Apples are a delicious and suitable option when it comes to boosting hemoglobin levels as they’re one of the most iron-rich fruits out there.

What level of hemoglobin is dangerously low?

  • What hemoglobin levels are considered severe or dangerously low? A hemoglobin level of less than 5.0 grams per deciliter (g/dl) is dangerous and could lead to heart failure or death. A normal hemoglobin level is 13.2–16.6 grams per deciliter (g/dL) for males and 11.6–15 g/dL for females.

Can I test my hemoglobin at home?

  • The BIOSAFEAnemia Meter is the first FDA-approved, hand-held device that can be conveniently used at home to test hemoglobin levels (Figure 1). Low levels of hemoglobin may indicate anemia. Thus, the Anemia Meter may be used as an additional screening method. It is not recommended for use in patients younger than 18.

What happens when your hemoglobin is low?

  • Anemia is a condition in which you lack enough healthy red blood cells to carry adequate oxygen to your body’s tissues. Having anemia, also referred to as low hemoglobin, can make you feel tired and weak. There are many forms of anemia, each with its own cause.

What does low hemoglobin cause?

  • A low hemoglobin count can also be due to blood loss, which can occur because of: Bleeding in your digestive tracts, such as from ulcers, cancers, or hemorrhoids. Frequent blood donation.

What is a healthy hemoglobin level by age?

  • 1-6 years: 9.5-14 g/dL. 6-18 years: 10-15.5 g/dL. Adult men: 14-18 g/dL. Adult women: 12-16 g/dL.

What is serum hemoglobin?

  • A serum hemoglobin test measures the amount of free-floating hemoglobin in your blood serum. The serum is the liquid that is left over when the red blood cells and the clotting elements have been removed from your blood plasma. Hemoglobin is a type of oxygen-carrying protein found in your red blood cells.

Is free hemoglobin toxic?

  • Hemoglobin is toxic to the human body. When the hemoglobin is encapsulated in the red blood cell it is a tetramer, but outside the red blood cell in the plasma, it breaks into two dimers that travel through the bloodstream quickly and create toxicity in the kidneys.

What causes elevated plasma-free hemoglobin?

  • Sharp spikes in plasma hemoglobin levels can indicate pump disruption. However, plasma hemoglobin can be artifactually increased due to a traumatic blood draw or prolonged exposure to post-draw RBCs.

What is the cost of a hemoglobin test?

  • Hemoglobin (Hb) Test Cost
CityAverage PricePrice Upto
AmritsarRs. 68.00Rs. 130.00
AnantapurRs. 101.00Rs. 130.00
AurangabadRs. 79.00Rs. 500.00
BangaloreRs. 94.00Rs. 650.00

What foods to avoid if you have low hemoglobin?

Foods to avoid
  • tea and coffee.
  • milk and some dairy products.
  • foods that contain tannins, such as grapes, corn, and sorghum.
  • foods that contain phytates or phytic acids, such as brown rice and whole-grain wheat products.
  • foods that contain oxalic acids, such as peanuts, parsley, and chocolate.

How can I raise my hemoglobin fast?

How to increase hemoglobin
  • in meat and fish.
  • soy products, including tofu and edamame.
  • eggs.
  • dried fruits, such as dates and figs.
  • broccoli.
  • green leafy vegetables, such as kale and spinach.
  • green beans.
  • nuts and seeds.

How do you fix low hemoglobin?

How is anemia treated?
  • Iron supplements are taken by mouth.
  • Foods are high in iron and foods that help your body absorb iron (like foods with Vitamin C).
  • Iron gave through an intravenous (IV) infusion. (This is often a choice if you have chronic kidney disease or CKD.)
  • Transfusions of red blood cells.

Does hemoglobin go down with age?

  • Results: Hemoglobin level was inversely associated with age, although this was more pronounced in men than in women.

What are two conditions that cause polycythemia?

  • The most common causes of secondary polycythemia include obstructive sleep apnea, obesity hypoventilation syndrome, and chronic obstructive pulmonary disease (COPD). Other causes include testosterone replacement therapy and heavy cigarette smoking.

What is the name of the hemoglobin test machine?

  • A hemoglobinometer is an instrument used to determine the hemoglobin content of the blood by spectrophotometric measurement.

What drink is high in iron?

  • You can quickly raise your iron levels by drinking iron-rich drinks like Aviva Romm’s iron tonic, spinach-cashew-raspberry smoothie, pumpkin juice, mulberry smoothie, and Prune juice. Eating dark green leafy vegetables, legumes, broccoli, fish, meat, and fresh citrus fruits will also help raise your iron levels.

Which fruit is best for hemoglobin?

  • Rely on Fruits: Apricots, apples, grapes, bananas, pomegranates, and watermelons play a very important role in improving hemoglobin count. Apples are a delicious and suitable option when it comes to boosting hemoglobin levels as they’re one of the most iron-rich fruits out there.

What level of hemoglobin is dangerously low?

  • What hemoglobin levels are considered severe or dangerously low? A hemoglobin level of fewer than 5.0 grams per deciliter (g/dl) is dangerous and could lead to heart failure or death. A normal hemoglobin level is 13.2–16.6 grams per deciliter (g/dL) for males and 11.6–15 g/dL for females.

Frequently Asked Questions

Is this article a replacement for a doctor?

No. It is educational content only. Patients should consult a qualified clinician for diagnosis and treatment.

When should I seek urgent care?

Seek urgent care for severe symptoms, rapidly worsening condition, breathing difficulty, severe pain, neurological changes, or any emergency warning sign.

References

Add references, clinical guidelines, textbooks, journal articles, or trusted medical sources here. You can edit this area later with a custom field named _rx_references.

Related Articles

Hemoglobin A1c Test

November 6, 202521 min read0 views

The hemoglobin A1c test—also known as glycated hemoglobin, glycosylated hemoglobin, HbA1c, or simply A1c—is used to measure an individual’s glucose control levels. The test shows average…

Read more

Orbital Decompression Surgery

August 18, 202518 min read0 views

Orbital decompression is an operation to make more room inside the eye socket. The eye socket is called the “orbit.” It is a cone-shaped…

Read more

Olfactory Nerve Disorders

May 8, 20248 min read0 views

Olfactory nerve disorders affect our sense of smell. This can impact our ability to enjoy food, detect danger like gas leaks, or even notice…

Read more

Written by Dr. Harun Ar Rashid, MD - Arthritis, Bones, Joints Pain, Trauma, and Internal Medicine Specialist

Dr. Md. Harun Ar Rashid, MPH, MD, PhD, is a highly respected medical specialist celebrated for his exceptional clinical expertise and unwavering commitment to patient care. With advanced qualifications including MPH, MD, and PhD, he integrates cutting-edge research with a compassionate approach to medicine, ensuring that every patient receives personalized and effective treatment. His extensive training and hands-on experience enable him to diagnose complex conditions accurately and develop innovative treatment strategies tailored to individual needs. In addition to his clinical practice, Dr. Harun Ar Rashid is dedicated to medical education and research, writing and inventory creative thinking, innovative idea, critical care managementing make in his community to outreach, often participating in initiatives that promote health awareness and advance medical knowledge. His career is a testament to the high standards represented by his credentials, and he continues to contribute significantly to his field, driving improvements in both patient outcomes and healthcare practices. Born and educated in Bangladesh, Dr. Rashid earned his BPT from the University of Dhaka before pursuing postgraduate training internationally. He completed his MD in Internal Medicine at King’s College London, where he developed a special interest in inflammatory arthritis and metabolic bone disease. He then undertook a PhD in Orthopedic Science at the University of Oxford, conducting pioneering research on cytokine signaling pathways in rheumatoid arthritis. Following his doctoral studies, Dr. Rashid returned to clinical work with a fellowship in interventional pain management at the Rx University School of Medicine, refining his skills in image-guided joint injections and minimally invasive pain-relief techniques.