Hemoglobin is a protein found in red blood cells that carries oxygen. The hemoglobin level in the blood varies based on age and gender, but it typically falls within a specific range. Foods that increase hemoglobin include iron-rich options like red meat, spinach, and lentils. Normal hemoglobin levels are generally 12–16 g/dL for adult women and 14–18 g/dL for men. Low hemoglobin levels are usually associated with anemia and reduce the body’s ability to carry oxygen.
What is Hemoglobin?
Hemoglobin is one of the key markers evaluated in a routine blood test (CBC or hemogram), often ordered by a doctor during illness or check-ups.
Hemoglobin is an iron-rich protein produced in the bone marrow and stored in red blood cells (erythrocytes). Oxygen from the air we breathe binds to hemoglobin and is transported to tissues throughout the body.
Carbon dioxide, produced in the tissues, binds to hemoglobin after oxygen is released and is carried back to the lungs to be exhaled. This vital circulation is made possible by hemoglobin’s oxygen transport function.
Each hemoglobin molecule can carry four oxygen molecules. In addition, hemoglobin helps red blood cells maintain their round shape, enabling smooth movement through blood vessels.
Since hemoglobin reflects iron levels in the body, it is the first parameter assessed in suspected anemia or iron deficiency. When hemoglobin is low, the most common diagnosis is anemia.
Symptoms like fatigue, dizziness, shortness of breath, and irregular heartbeat may indicate low hemoglobin. Elevated levels may result from blood disorders, smoking, or dehydration.
A sharp decrease in hemoglobin impairs the body’s ability to carry oxygen and must be closely monitored, especially before and after surgeries. Whether a patient needs a blood transfusion is often based on their hemoglobin level.
Causes of Low Hemoglobin (HGB)
Low hemoglobin may signal an underlying disease. The degree of decrease determines the treatment approach. Mildly low levels may not cause symptoms, but severe drops can lead to fatigue, paleness, anxiety, palpitations, poor appetite, hair loss, and brittle nails.
The most common cause is anemia. Causes include:
Iron-deficiency anemia: due to poor iron intake, poor iron absorption, or chronic blood loss
Blood loss: from wounds, ulcers, cancers, hemorrhoids, frequent blood donation, or menstruation
Vitamin B12 or folic acid deficiency: affects red blood cell production or shape
Hemolytic anemia: caused by destruction of red blood cells due to disease
Hemoglobin structure disorders: inherited conditions affecting hemoglobin synthesis
Medications: certain drugs may impair red blood cell production
Formula-fed infants: breast milk is rich in iron; lack of it may lead to low hemoglobin
Pregnancy: increased iron needs during pregnancy may lead to deficiency
High Hemoglobin (HGB) Levels
Elevated hemoglobin may also cause issues, including:
Itching, headaches, dizziness
Excessive sweating
Painful joint swelling
Weight loss
Yellowing of the eyes
Fatigue
One potential cause is polycythemia, a condition in which the body produces too many red blood cells, making the blood thick and increasing the risk of clotting, heart attack, or stroke.
Other causes include:
Lung diseases
Dehydration
Living at high altitudes
Smoking or tobacco use
Fever, vomiting, or excessive physical exertion
If you’ve been diagnosed with polycythemia and hemoglobin remains high despite treatment, your care plan may need adjustment.
Hemoglobin in Pregnancy
Hemoglobin levels are especially critical during pregnancy. Too high a level can increase the risk of stillbirth, while too low can raise the risk of miscarriage.
Expected values in pregnancy:
11–14 g/dL
Should not drop below 11 g/dL in the 1st and 3rd trimesters
Should not fall below 10.5 g/dL in the 2nd trimester