Hemoglobin Normal Range by Age (and Sex): Full Reference Chart

Hemoglobin is the iron-rich protein in your red blood cells that carries oxygen from your lungs to the rest of your body. When a complete blood count (CBC) reports your hemoglobin, the number is judged against a reference range that shifts with age and sex. A value that is perfectly normal for a newborn would signal a problem in an adult, and what counts as low for a man may be fine for a woman. This guide lays out the real reference values, why they change, and when an out-of-range result deserves attention.

Part of our Complete Blood Count guide.

What is a normal hemoglobin level?

For a healthy adult, a normal hemoglobin level is roughly 13.8 to 17.2 g/dL in men and 12.1 to 15.1 g/dL in women, based on MedlinePlus reference values. Hemoglobin (often written Hgb or Hb) is measured in grams per deciliter of blood (g/dL), and it is one of the core numbers on a standard CBC.

There is no single universal cutoff. Each laboratory sets its own reference range based on the population it serves and the analyzer it uses, so your report may say 13.5 to 17.5 g/dL or 12.0 to 16.0 g/dL and still be correct. That is why MedlinePlus notes that “normal value ranges may vary slightly among different laboratories.” The practical rule is simple: read your result against the range printed on your own lab report, then talk with your clinician about anything flagged high or low.

Why the range matters: hemoglobin tracks how much oxygen your blood can move. Too little can leave you tired and short of breath, while too much can thicken the blood, so the reference range is a guardrail, not a grade.

Hemoglobin normal range by age

Hemoglobin reference ranges change dramatically across the lifespan, from a high of about 14 to 24 g/dL at birth down to roughly 9.5 to 14 g/dL in early infancy before rising again, per MedlinePlus and UCSF Benioff Children’s Hospital. The table below gathers commonly cited reference values. Treat them as typical ranges, not strict pass-or-fail lines, because labs differ.

Notice the U-shaped pattern. Babies are born with very high hemoglobin because the womb is a low-oxygen environment, then levels fall to a natural low point called the “physiologic nadir” around 2 to 3 months of age as fetal red cells break down and production catches up. From there, hemoglobin climbs steadily through childhood. Sex differences appear during puberty and persist into adulthood.

How does sex change the range?

Sex shifts the adult hemoglobin range by roughly 1 to 2 g/dL, with men sitting higher (about 13.8 to 17.2 g/dL) than women (about 12.1 to 15.1 g/dL), according to MedlinePlus. Before puberty, boys and girls share nearly identical ranges. The gap opens during adolescence and holds for most of adult life.

Two main drivers explain the difference. First, testosterone stimulates red blood cell production, nudging male hemoglobin upward. Second, menstruation causes regular iron and blood loss in many women, which tends to pull hemoglobin down. This is also why anemia thresholds differ by sex: the World Health Organization places the anemia line at below 13 g/dL for men and below 12 g/dL for non-pregnant women.

Pregnancy is a special case. Blood volume expands faster than red cell mass, diluting hemoglobin, so a value near 11 g/dL can be expected in pregnancy. The CDC commonly uses 11 g/dL as the lower limit in the first and third trimesters. Pregnant patients should follow trimester-specific guidance from their own clinician.

What makes hemoglobin rise or fall with age?

Hemoglobin tends to drift slightly downward in older adults, and studies cited by NIH-indexed research suggest anemia becomes more common after age 65, affecting more than 10 percent of community-dwelling seniors. Aging itself does not automatically lower hemoglobin into the anemic range, but the causes of low values become more frequent with age.

Several factors push hemoglobin up or down at any age:

• Iron, B12, and folate: shortfalls of any of these reduce red cell production and lower hemoglobin.
• Kidney function: the kidneys make erythropoietin, the hormone that signals red cell production, so chronic kidney disease often lowers hemoglobin.
• Blood loss: heavy periods, ulcers, or gastrointestinal bleeding deplete hemoglobin over time.
• Chronic disease and inflammation: long-term conditions can suppress red cell production.
• High altitude and smoking: both raise hemoglobin as the body compensates for lower oxygen, and MedlinePlus notes levels rise for several weeks at higher altitude.
• Dehydration: a falsely high reading can occur because the blood is more concentrated.

Because so many variables move the number, one out-of-range result is a prompt to investigate, not a diagnosis on its own.

When is an out-of-range result a concern?

An out-of-range hemoglobin is most concerning when it pairs with symptoms or when it falls clearly past the anemia or high-hemoglobin thresholds. The Cleveland Clinic considers hemoglobin high above roughly 16.5 g/dL in adult men and above 16 g/dL in adult women, while the WHO marks anemia below 13 g/dL in men and below 12 g/dL in non-pregnant women.

Low hemoglobin (anemia) often shows up as fatigue, weakness, pale skin, shortness of breath, dizziness, or a fast heartbeat. Mild cases may cause nothing at all and turn up only on a routine CBC. Common causes include iron deficiency, blood loss, and chronic disease.

High hemoglobin can stem from dehydration, smoking, lung or heart conditions, living at altitude, or a bone marrow disorder such as polycythemia vera. It may thicken the blood and raise clotting risk. A single borderline value usually warrants a repeat test, while a markedly abnormal result, or any abnormal value with symptoms, should be reviewed promptly by a clinician who can order follow-up testing such as iron studies, a reticulocyte count, or kidney function tests.

Frequently asked questions

Is 12 g/dL a normal hemoglobin level?

For an adult woman, 12.1 g/dL sits at the low end of normal per MedlinePlus. For an adult man it is below the typical range and may indicate mild anemia, since the WHO anemia cutoff for men is 13 g/dL. Context and symptoms matter, so confirm with your clinician.

What hemoglobin level is dangerously low?

Hemoglobin below about 7 to 8 g/dL is often considered severe and may prompt a blood transfusion, depending on symptoms and the cause. Any level under your lab’s range deserves evaluation, but values this low warrant urgent medical attention, especially with chest pain or breathlessness.

Does hemoglobin naturally decrease with age?

Hemoglobin tends to dip slightly in older adults, and anemia is more common after age 65. However, aging alone should not drop you into the anemic range. A low value in a senior usually points to an underlying cause worth investigating, not simply “old age.”

Why is my hemoglobin different from my friend’s normal?

Reference ranges vary by age, sex, and laboratory. Men typically run 1 to 2 g/dL higher than women, and each lab calibrates its own range. Always compare your result to the range printed on your own report rather than someone else’s.

Can dehydration raise hemoglobin?

Yes. Dehydration concentrates the blood, which can make hemoglobin look falsely high. Rehydrating and repeating the test often returns the value to normal. This is why clinicians frequently retest a single high reading before pursuing further workup.

Sources

• MedlinePlus, Hemoglobin Medical Encyclopedia
• UCSF Benioff Children’s Hospital, Hemoglobin
• Labcorp, Pediatric Testing Reference Ranges
• Cleveland Clinic, High Hemoglobin Count
• Cleveland Clinic, Anemia
• World Health Organization, Guideline on Haemoglobin Cutoffs for Anaemia

This article is for general educational purposes and is not medical advice. It cannot diagnose or treat you and does not replace your clinician. Always discuss your lab results and any health decisions with a qualified healthcare professional.