Hemoglobin, sometimes abbreviated as Hgb, is a protein in red blood cells that carries iron. This iron holds oxygen, making hemoglobin an essential component of your blood. When your blood doesn’t contain enough hemoglobin, your cells don’t receive enough oxygen.
Doctors determine your hemoglobin level by analyzing a sample of your blood. A variety of factors affect your hemoglobin levels, including your:
- medical history
Keep reading to learn more about what’s considered a normal, high, and low hemoglobin level.
In adults, the average hemoglobin level is slightly higher for men than it is for women. It’s measured in grams per deciliter (g/dL) of blood.
|Sex||Normal hemoglobin level (g/dL)|
|Female||12 or higher|
|Male||13 or higher|
Older adults also tend to have lower hemoglobin levels. This may be due to several factors, including:
- lower iron levels due to chronic inflammation or poor nutrition
- medication side effects
- high rates of chronic diseases, such as kidney disease
Infants tend to have higher average hemoglobin levels than adults. This is because they have higher oxygen levels in the womb and need more red blood cells to transport the oxygen. But this level starts to go down after several weeks.
|Age||Female range (g/dL)||Male range (g/dL)|
High hemoglobin levels generally accompany high red blood cell counts. Remember, hemoglobin is found in red blood cells, so the higher your red blood cell count, the higher your hemoglobin level and vice versa.
A high red blood cell count and hemoglobin level can indicate several things, including:
- Congenital heart disease. This condition can make it hard for your heart to effectively pump blood and deliver oxygen throughout your body. In response, your body sometimes produces additional red blood cells.
- Dehydration. Not having enough fluid can cause red blood cell counts to appear higher because there isn’t as much fluid to balance them.
- Kidney tumors. Some kidney tumors stimulate your kidneys to make excess erythropoietin, a hormone that stimulates red blood cell production.
- Lung disease. If your lungs aren’t working effectively, your body may try to produce more red blood cells to help carry oxygen.
- Polycythemia vera. This condition causes your body to produce extra red blood cells.
You may also be more likely to have high hemoglobin levels if you:
- have a family history of disorders that affect red blood cell counts, such as altered oxygen sensing
- live at a high altitude
- recently received a blood transfusion
A low hemoglobin level is usually seen with low red blood cell counts.
Some medical conditions that can cause this include:
- Bone marrow disorders. These conditions, such as leukemia, lymphoma, or aplastic anemia, can all cause low red blood cell counts.
- Kidney failure. When your kidneys aren’t functioning properly, they don’t produce enough of the hormone erythropoietin that stimulates red blood cell production.
- Uterine fibroids. These are tumors that usually aren’t cancerous, but they can cause significant bleeding, leading to lower red blood cell counts.
- Conditions that destroy red blood cells. These include sickle cell anemia, thalassemia, G6PD deficiency, and hereditary spherocytosis.
You may also be more likely to have low hemoglobin levels if you:
- have a condition that causes chronic bleeding, such as gastric ulcers, colon polyps, or heavy menstrual periods
- have a folate, iron, or vitamin B-12 deficiency
- are pregnant
- were involved in a traumatic accident, such as a car accident
When having blood work done, you might also see results for hemoglobin A1c (HbA1c), sometimes called glycated hemoglobin. An HbA1c test measures the amount of glycated hemoglobin, which is hemoglobin that has glucose attached to it, in your blood.
Doctors often order this test for people with diabetes. It helps to give a clearer picture of someone’s average blood glucose levels over the course of 2 to 4 months. Glucose, also called blood sugar, circulates throughout your blood and attaches to hemoglobin.
The more glucose in your blood, the more likely you are to have higher levels of glycated hemoglobin. The glucose stays attached to the hemoglobin for about 120 days. A high HbA1c level indicates that someone’s blood sugar has been high for several months.
In most cases, someone with diabetes should aim for an HbA1c level of 7 percent or less. Those without diabetes tend to have HbA1c levels of about 5.7 percent. If you have diabetes and a high HbA1c level, you may need to adjust your medication.
Hemoglobin levels can vary by gender, age, and medical condition. A high or low hemoglobin level can indicate a variety of things, but some people just have naturally higher or lower levels.
Your doctor will look at your results in the context of your overall health to determine whether your levels indicate an underlying condition.