Hemoglobin

Hemoglobin (Hb) measures the oxygen-carrying protein inside your red blood cells, and it is one of the core numbers on any complete blood count. A normal level runs roughly 14.0 to 17.5 g/dL for adult men and 12.3 to 15.3 g/dL for adult women.

Ranges vary between labs, so compare to the range on your own lab report.

What hemoglobin measures

Hemoglobin is the iron-rich protein in red blood cells that binds oxygen in your lungs and delivers it to tissues throughout your body. The test reports the concentration of that protein in your blood in grams per deciliter. Because it tracks closely with your red cell mass, it is a primary marker of how well your blood can carry oxygen.

What high or low levels mean

Low hemoglobin defines anemia. Common causes include iron deficiency, vitamin B12 or folate deficiency, acute or chronic blood loss such as heavy periods or gastrointestinal bleeding, and chronic diseases including kidney disease and inflammation. Symptoms can include fatigue, shortness of breath, pale skin, and dizziness.

High hemoglobin most often reflects dehydration, which concentrates the blood. It can also point to chronic low-oxygen states such as smoking, sleep apnea, high-altitude living, or lung and heart disease, and less commonly to polycythemia vera, a bone marrow disorder.

Follow up with a clinician if your level falls outside your lab's range, especially with symptoms or a rapid change from prior results.

Hemoglobin FAQ

What is a dangerously low hemoglobin level?

Levels below about 8 g/dL are generally considered severe and may cause marked fatigue, breathlessness, or a fast heartbeat. Values this low often prompt urgent evaluation and sometimes a transfusion, depending on your symptoms and how quickly the drop occurred.

Can dehydration raise your hemoglobin?

Yes. When you are dehydrated, plasma volume drops and your blood becomes more concentrated, so hemoglobin reads higher than your true baseline. Rehydrating usually returns the value to normal, which is why testing conditions and hydration status matter for interpretation.

What is the difference between hemoglobin and hematocrit?

Hemoglobin measures the oxygen-carrying protein concentration, while hematocrit measures the percentage of your blood volume made up of red cells. They move together and are often interpreted side by side to assess anemia or red cell excess.

Read alongside red blood cell count, hematocrit, ferritin, and the complete blood count.

Sources

• Cleveland Clinic. Low Hemoglobin: Causes, Signs and Treatment.

• Billett HH. Hemoglobin and Hematocrit. Clinical Methods, NCBI Bookshelf.