Hemoglobin is a protein in red blood cells that carries oxygen from the lungs to tissues and organs in the body. The normal range for hemoglobin is generally between 12-16 grams per deciliter (g/dL) for men, and 12-15 g/dL for women. When hemoglobin levels fall below the normal range, it is called anemia. There are several potential causes for low hemoglobin or anemia, which this article will explore in detail.
What is hemoglobin?
Hemoglobin is comprised of four protein subunits – two alpha globin and two beta globin chains. Each of these chains binds with an iron-containing heme group, which gives blood its red color and allows hemoglobin to bind and transport oxygen. Hemoglobin picks up oxygen as red blood cells travel through the lungs, then releases the oxygen as the blood circulates to tissues that need it.
Hemoglobin makes up about 33% of the total content of red blood cells. Since red blood cells primarily function to deliver oxygen, the hemoglobin level reflects the oxygen-carrying capacity of your blood. When hemoglobin is low, your body doesn’t get enough oxygen to function optimally.
What are normal hemoglobin levels?
Normal ranges for hemoglobin levels are:
- Newborns: 17-22 g/dL
- Children: 11-13 g/dL
- Adult males: 13.5-17.5 g/dL
- Adult females: 12-15.5 g/dL
- Pregnant females: 11-12 g/dL
Levels under 12-13 g/dL for men and under 11-12 g/dL for women signify anemia. The lower the hemoglobin, the more severe the anemia.
What causes low hemoglobin?
There are several potential causes of low hemoglobin levels, including:
Iron deficiency
Iron deficiency is the most common cause of anemia worldwide. Iron is an essential component of hemoglobin. Without adequate iron, the body cannot produce enough hemoglobin for red blood cells.
Causes of iron deficiency include:
- Inadequate dietary iron intake
- Poor absorption of iron from foods due to celiac disease or other digestive disorders
- Pregnancy – increased iron demands
- Heavy menstrual bleeding
- Internal bleeding, often from stomach ulcers or colon cancer
- Frequent blood donations
Vitamin deficiency
Deficiencies in folate, vitamin B12, and vitamin B6 can disrupt hemoglobin production and lead to anemia.
Causes include:
- Diet low in fruits, vegetables, meat that provide these vitamins
- Poor nutrient absorption
- Alcoholism
Bone marrow disorders
Bone marrow is responsible for producing red blood cells and hemoglobin. Problems with the bone marrow can cause low hemoglobin.
Causes include:
- Leukemia and myelodysplastic syndromes – crowd out healthy cells
- Aplastic anemia – bone marrow can’t produce enough blood cells
- Chemotherapy and radiation damage bone marrow
Bleeding disorders
Excessive bleeding depletes the body of red blood cells and hemoglobin. This may occur in hemorrhagic conditions like:
- Ulcers
- Trauma
- Gastrointestinal bleeding
- Menstrual bleeding
- Childbirth
- Surgery
- Anticoagulant medications
Hemoglobin disorders
Genetic defects in hemoglobin such as sickle cell anemia and thalassemia interfere with hemoglobin production and function. The abnormal hemoglobin can’t effectively carry oxygen.
Chronic diseases
Many chronic illnesses indirectly cause anemia by impairing absorption of nutrients needed for hemoglobin formation. These include:
- Kidney failure
- Cancer
- HIV/AIDS
- Rheumatoid arthritis
- Heart failure
- Liver disease
Inflammatory illnesses like these also disrupt iron metabolism and erythropoiesis, the process of red blood cell production.
Inflammation
Chronic inflammation shuts down iron absorption and suppresses erythropoiesis. Diseases associated with inflammation include:
- Rheumatoid arthritis
- Inflammatory bowel disease
- Lupus
- Tuberculosis
- Infections
Symptoms of low hemoglobin
Signs and symptoms of anemia or low hemoglobin levels include:
- Fatigue, weakness
- Shortness of breath with activity
- Rapid heartbeat
- Pale skin
- Dizziness or lightheadedness
- Headaches
- Chest pain
- Cold hands and feet
The symptoms reflect inadequate oxygen delivery to tissues and the heart’s attempt to compensate with a faster heart rate. In mild anemia, there may be no symptoms. More severe anemia produces noticeable fatigue, exercise intolerance, and functional impairment.
Who is at risk for low hemoglobin?
Those at increased risk for anemia include:
- Women of childbearing age
- Pregnant women
- Young children and adolescents
- Older adults
- People with chronic diseases like cancer, kidney failure, HIV/AIDS
- Those with gastrointestinal disorders that impair nutrient absorption like celiac or Crohn’s disease
- People with bleeding disorders or ulcers
- Vegetarians, vegans, or those with very restricted diets
Anemia is twice as common in females due to menstruation and pregnancy. Up to 50% of chemotherapy patients develop anemia. In older adults, anemia prevalence ranges from 8-44%.
Diagnosing low hemoglobin
Low hemoglobin is diagnosed with a complete blood count (CBC) test. This simple blood test measures red blood cell count, hemoglobin level, and other values. Additional testing can help determine the cause:
- Iron studies – assess iron levels and iron deficiency
- Vitamin levels – B12, folate and other vitamins
- Stool tests – check for blood loss
- Bone marrow biopsy – examine blood cell production
- Hemoglobin electrophoresis – diagnose hemoglobinopathy
- Blood loss evaluation – test for bleeding disorders
The CBC provides key information about red blood cell size and hemoglobin content that can point to a diagnosis.
Increasing low hemoglobin levels
Treatment focuses on addressing the underlying cause:
- Iron supplements – for iron deficiency anemia
- Vitamin supplements – B12, folic acid, etc for deficiencies
- Diet changes – increased iron and nutrient-rich foods
- Treat bleeding – medications, endoscopy, surgery
- Treat GI disorders – improve nutrient absorption
- Transfusions – in severe anemia
- Treat chronic diseases – HIV, kidney failure, etc
- Erythropoiesis-stimulating agents – man-made versions of erythropoietin to stimulate RBC production
- Immunosuppressants – for anemia of chronic inflammation
- Chemotherapy – for bone marrow disorders
Iron supplementation is used to correct most cases of iron deficiency anemia. Vitamin supplements treat deficiencies. Underlying gastrointestinal or inflammatory conditions must be properly managed. Severe anemia requires blood transfusions to rapidly boost hemoglobin levels.
With appropriate treatment, hemoglobin levels usually recover within 1-2 months. Any persistent anemia warrants further investigation. Lifelong treatment may be needed for chronic conditions causing anemia.
Preventing low hemoglobin
Preventive strategies for anemia include:
- Eat iron-rich foods – meat, eggs, leafy greens, beans, lentils
- Ensure adequate folic acid, B12, vitamin C – citrus fruits and juices
- Treat underlying medical conditions
- Minimize bleeding risks – avoid excess aspirin, treat ulcers
During pregnancy, take iron supplements as recommended. Those with iron deficiency anemia should take regular iron supplements to replenish iron stores, even after hemoglobin levels normalize. People with anemia associated with intestinal disorders may require vitamin B12 injections for life.
Regular primary care visits provide opportunities to screen for and diagnose anemia early. Treatment can then begin before symptoms progress.
Conclusion
Hemoglobin carries oxygen from the lungs to tissues and organs throughout the body. A hemoglobin level below the normal range indicates anemia or low red blood cell counts. There are many potential causes, including iron deficiency, vitamin deficiencies, chronic diseases, bleeding disorders, bone marrow problems, and genetic hemoglobin defects.
Symptoms of anemia include fatigue, shortness of breath, dizziness, and paleness. It is diagnosed with a complete blood count test. Treatment involves identifying and addressing the underlying cause, which may include iron supplements, vitamin supplements, medications, transfusions, diet changes, or surgery. Preventing anemia centers around an iron-rich diet and treating any chronic medical conditions.
Low hemoglobin reduces oxygen delivery in the body and can produce significant symptoms and health impairment. Prompt diagnosis and treatment of anemia is essential to restore hemoglobin levels and relieve symptoms. With appropriate care, hemoglobin levels can generally be returned to the normal range.