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Hemoglobin
The iron-rich protein in red blood cells that carries oxygen from the lungs to every tissue. The core marker checked whenever anemia is suspected.
Other names: Hb, Hgb, H&HSection: Blood cells
Updated: August 29, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortHemoglobin carries oxygen in the blood. Typical adult reference ranges are 13.8–17.2 g/dL (138–172 g/L) for men and 12.1–15.1 g/dL (121–151 g/L) for women. A low level points toward anemia; a high level usually reflects long-term low oxygen, smoking, or dehydration. It is measured as part of a complete blood count (CBC).
Reference ranges
Group
Reference range
Men
13.8–17.2 g/dL (138–172 g/L)
Women
12.1–15.1 g/dL (121–151 g/L)
Newborns
14–24 g/dL (140–240 g/L)
Infants
9.5–14 g/dL (95–140 g/L)
Adult and pediatric values above are the common reference ranges quoted in the MedlinePlus Medical Encyclopedia. Intervals differ between laboratories, and pregnancy lowers the expected range — the report's own reference column applies.
Check your value
Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.
A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.
What this marker is
Hemoglobin is the protein inside red blood cells that picks up oxygen in the lungs and delivers it to tissues; on the way back it carries part of the carbon dioxide. Cells need that oxygen to grow, reproduce, and produce energy.
The hemoglobin level says a lot about the health of red blood cells overall. If it is abnormal, that can be a sign of a blood disorder. The test is almost never ordered alone: it is one line of the complete blood count (CBC), which counts and describes all the cells in the blood.
One clarification prevents a common mix-up: a hemoglobin test is not the same as a hemoglobin A1C test. The first measures how much hemoglobin is in the blood right now; the second shows what share of it is coated with glucose, as an average over two to three months.
Providers order the test during routine exams and whenever anemia is on the table — for weakness, dizziness, or cold hands and feet; for a family history of thalassemia or sickle cell anemia; for a diet low in iron; for long-term infections; or after significant blood loss from an injury or surgery.
When it is high
Long-term low blood oxygen (hypoxia)The most common driver. The body compensates for chronic oxygen shortage by producing more red blood cells — typical of chronic lung disease, pulmonary fibrosis, congenital heart disease, and right heart failure (cor pulmonale).
Cigarette smokingCarbon monoxide in smoke occupies hemoglobin, and the body answers by making more of it.
DehydrationWith less fluid in the blood — for example after severe diarrhea — the same amount of hemoglobin sits in a smaller volume, so the concentration rises.
Polycythemia veraA bone marrow disease that produces red blood cells in excess, raising hemoglobin directly.
High altitudeHemoglobin increases for several weeks after moving to higher ground — a normal adaptation to thinner air.
When it is low
BleedingObvious blood loss after an injury or surgery, or slow hidden bleeding in the digestive tract.
Too little iron, folate, or vitamin B12Without these building blocks the bone marrow cannot finish hemoglobin and red blood cell production.
Chronic illness and kidney diseaseLong-standing inflammation and chronic kidney disease both suppress red blood cell production.
Bone marrow problemsLeukemia, other cancers, drug toxicity, radiation, or infection can leave the marrow unable to produce new red cells.
PregnancyThe blood volume expands faster than red cell production, so hemoglobin normally dips — a physiological change rather than a disease.
Destruction of red blood cells (hemolysis)Cells are broken down faster than the marrow can replace them.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
No special preparation is needed for the hemoglobin test itself. If other blood tests are ordered at the same time, a few hours of fasting may be requested for those — the provider's instructions say which applies.
When a retest makes sense
A result slightly outside the range is often re-checked before conclusions, especially if the draw happened during dehydration or right after an illness. During anemia treatment, hemoglobin is the number that shows whether the therapy is working; it is also monitored when medicines that can lower blood counts are used.
Who usually reviews this result
A result outside the reference range is usually reviewed by: your GP or primary care doctor; a hematologist if a blood disorder is suspected. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: HemoglobinHbHgbH&HHaemoglobin
Units and conversion
Measured in: g/dL
g/dL=g/L
g/dL × 10 = g/L. Example: 14.0 g/dL = 140 g/L. Results are rounded to 2 decimal places.
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
No. Iron is a mineral; hemoglobin is the protein built with it. Iron deficiency usually shows up first in ferritin (the storage marker) and only later drags hemoglobin down. That is why both can appear on the same order.
Why is hemoglobin high in smokers?
Carbon monoxide from cigarette smoke binds to hemoglobin and blocks its oxygen-carrying capacity. The body compensates by producing more hemoglobin and more red blood cells. The value looks high on paper while oxygen delivery is actually impaired.
What is the difference between hemoglobin and hematocrit?
Hemoglobin is the amount of the oxygen-carrying protein itself; hematocrit is the share of blood volume occupied by red blood cells. Both come from the same CBC sample and usually move together.
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