Hemoglobin Levels Chart: Normal Ranges by Age and Sex, Plus WHO Anemia Cutoffs

A hemoglobin result is a single number, but whether it is “normal” depends on your age, your sex, whether you are pregnant, and even where you live. This hemoglobin levels chart pulls the key numbers into one place: the reference ranges laboratories use, the World Health Organization (WHO) cutoffs that define anemia, and the severity grades below them. In US reports, hemoglobin is measured in grams per deciliter (g/dL). Much of the rest of the world uses grams per liter (g/L) — simply multiply g/dL by 10, so 13.5 g/dL is 135 g/L.

For a quick answer: the typical reference range is 13.5 to 17.5 g/dL for adult men and 12.0 to 15.5 g/dL for adult women, though every laboratory sets its own limits and the range printed on your report is the one that applies to you. The sections below explain where those numbers come from and what a result outside them usually means.

What hemoglobin is and what the test measures

Hemoglobin is the protein inside red blood cells that does the actual work of carrying oxygen. Each hemoglobin molecule contains iron, and it picks up oxygen in the lungs, travels with it through the bloodstream, and releases it to the organs and tissues that need it. On the return trip it carries the waste gas carbon dioxide back to the lungs to be breathed out, as the Mayo Clinic  explains. When hemoglobin is low, every part of the body gets less oxygen than it should, which is why the symptoms of anemia are so wide-ranging.

A hemoglobin test measures the concentration of this protein in a blood sample. It is almost never ordered on its own: it comes as part of a complete blood count (CBC), the standard panel run at checkups and whenever symptoms such as fatigue, weakness, shortness of breath or dizziness need an explanation. If blood is drawn only for hemoglobin, you do not need to fast beforehand.

One result is a snapshot, not a diagnosis. Clinicians read it alongside the range printed by your own laboratory, the trend across your previous tests, and companion CBC values such as hematocrit, MCV (average red cell size) and ferritin (iron stores). A value just outside the range in someone who feels well is often simply rechecked; a value far outside it, or one that is falling, needs a cause.

Hemoglobin levels chart: normal reference ranges by age and sex

The table below shows the reference ranges in common use. A reference range is the band that covers the central 95% of results in healthy people tested by a laboratory, which means about 1 in 20 completely healthy people will land just outside it. Ranges are highest at birth, fall through infancy, climb again through childhood, and split by sex from puberty onward, because testosterone stimulates red cell production in men while menstrual blood loss lowers iron stores in women.

Individual laboratories draw their lines a little differently. The Mayo Clinic, for example, uses a tighter healthy range of 13.2 to 16.6 g/dL for men and 11.6 to 15.0 g/dL for women. Neither set of numbers is “wrong”: each lab builds its range from its own equipment and reference population. This is why a result flagged low at one laboratory can be unremarkable at another, and why the range on your own report always wins over a chart on the internet — including this one.

Hemoglobin in pregnancy: why the range drops

Pregnancy changes the maths. Blood volume expands by roughly half during pregnancy, and the liquid part (plasma) expands more than the red cell mass does, so the same amount of hemoglobin is diluted in more fluid and the measured level falls even when nothing is wrong. The dip is deepest in the second trimester, and iron demand rises at the same time because the baby and placenta need iron too.

Because of this, the WHO sets separate anemia cutoffs by trimester in its 2024 guideline on haemoglobin cutoffs . Below these levels, a pregnant woman is considered anemic and the cause — most often iron deficiency — should be looked for and treated.

WHO anemia chart: cutoffs and severity grades

Laboratory ranges describe what is typical; the WHO cutoffs define what counts as anemia, and how serious it is. The table below is the WHO’s 2024 severity classification, converted from g/L to g/dL. It applies to people living at sea level who do not smoke — the WHO adjusts the cutoffs upward for altitude and smoking, as explained further down.

Notice one subtlety: the WHO anemia cutoff for men (13.0 g/dL) sits below the lower limit many US laboratories print (13.5 g/dL). A man with a result of 13.2 g/dL may see it flagged as low on his report yet does not meet the WHO definition of anemia. Both are doing different jobs — the lab range describes his local reference population, the WHO line standardizes diagnosis and statistics — and a result in that grey zone is a reason to watch the trend and check iron stores, not a reason to panic.

Hemoglobin vs hematocrit: what is the difference?

Hemoglobin and hematocrit appear side by side on every CBC and are often confused, but they measure different things. Hemoglobin is the weight of oxygen-carrying protein per deciliter of blood. Hematocrit is the percentage of your blood volume that is taken up by red blood cells. Typical adult hematocrit ranges are about 41% to 50% for men and 36% to 44% for women, per the Cleveland Clinic.

The two track each other closely: as a rule of thumb, hematocrit (%) is roughly 3 times the hemoglobin value (g/dL), so a hemoglobin of 14 g/dL pairs with a hematocrit near 42%. They can drift apart, though. Most analyzers calculate hematocrit from the red cell count and the average cell size (MCV), so conditions that make red cells unusually small or large can separate the two numbers. Shifts in blood fluid volume — dehydration, for example — push both in the same direction. For diagnosing and grading anemia, hemoglobin is the value guidelines use.

Low hemoglobin: causes and symptoms

A hemoglobin below the reference range is called anemia. Anemia is a sign, not a diagnosis in itself — the job is to find out why. Causes fall into three broad groups: losing blood, not making enough red cells or hemoglobin, and breaking red cells down too quickly.

Blood loss is the most common route. It can be obvious, such as heavy menstrual periods or visible bleeding, or silent, such as slow bleeding from the stomach or bowel from an ulcer, polyps or hemorrhoids. Because blood carries iron out of the body, chronic blood loss is also the most common cause of iron deficiency in adults.

Underproduction covers the nutritional deficiencies — too little iron, vitamin B12 or folate — as well as problems that stop the bone marrow keeping up. Long-term inflammation from chronic disease can lock iron away where the marrow cannot use it, chronic kidney disease reduces production of erythropoietin (the hormone that tells the marrow to make red cells), and marrow disorders such as leukemia directly crowd out production. Inherited conditions such as thalassemia make hemoglobin itself abnormal from birth. Iron deficiency alone is common enough that its early signs are worth knowing: our guide to iron deficiency symptoms walks through them.

Symptoms of low hemoglobin tend to creep in as the level falls, and how fast it falls matters as much as the number: a sudden drop is felt far more than the same level reached slowly. Common symptoms include:

• Fatigue, weakness and reduced stamina
• Pale skin, lips and inner eyelids
• Shortness of breath on exertion and rapid or pounding heartbeat
• Dizziness, light-headedness and headaches
• Cold hands and feet
• Brittle nails, or nails that curve upward into a spoon shape — our iron deficiency nail health chart shows what to look for
• Unusual cravings for ice, starch or other non-food items (pica), a classic iron deficiency clue

Many people with mild anemia feel nothing at all, which is why it is so often found by a routine blood test rather than by symptoms.

High hemoglobin: causes

A hemoglobin persistently above the reference range is called erythrocytosis. The first question is whether the blood is genuinely richer in red cells or simply more concentrated. Dehydration — from vomiting, diarrhea, heavy sweating, burns or simply not drinking enough — removes fluid from the blood and makes every concentration, hemoglobin included, read high. That type corrects when fluid balance is restored.

True increases happen when the body is driven to make more red cells, usually because it senses too little oxygen. Causes include living at high altitude, smoking (carbon monoxide locks up hemoglobin, so the body compensates by making more), chronic lung disease such as COPD, sleep apnea, some heart conditions, and tumors that secrete erythropoietin. Testosterone treatment and injected erythropoietin have the same effect. The Cleveland Clinic  flags adult levels above about 17.5 g/dL in men and 15.3 g/dL in women, with hematocrit above 50% and 45% respectively, as erythrocytosis.

The cause that changes management most is polycythemia vera, a bone marrow disorder in which red cells are overproduced without an oxygen signal, usually driven by a JAK2 gene mutation. Hematologists start evaluating for it at lower levels than the top of the lab range: a hemoglobin above 16.5 g/dL in men or 16.0 g/dL in women (or hematocrit above 49% in men, 48% in women) is one of the WHO diagnostic criteria. It matters because overly thick blood raises the risk of clots, stroke and heart attack. A single high reading is usually repeated first — dehydration and a tight tourniquet can both nudge a result up — but a level that stays high needs an explanation.

What can shift your result: altitude, smoking, hydration and pregnancy

Several everyday factors move a hemoglobin result by enough to cross a cutoff, which is why the WHO publishes adjustments for two of them.

Altitude. The higher you live, the thinner the air and the more hemoglobin your body makes to compensate. The WHO raises the anemia cutoff for people at altitude by the amounts below (equivalently, that amount is subtracted from the measured value before it is compared with the sea-level chart).

Smoking. Carbon monoxide in cigarette smoke binds hemoglobin and takes it out of service, so smokers run higher levels to compensate. The WHO adjusts the anemia cutoff upward by about 0.3 g/dL for people who smoke, which means a smoker can be anemic at a hemoglobin that looks acceptable on the standard chart.

Hydration and timing. Dehydration concentrates the blood and pushes the result up; being well hydrated — and pregnancy, discussed above — dilutes it and pushes it down. Smaller effects come from posture and the time of day. And after major blood loss, the hemoglobin can look deceptively normal for the first hours, before fluid shifts reveal the true drop. All of this is why clinicians interpret one number in context rather than in isolation.

When to see a doctor

Book a routine follow-up for any result outside your laboratory’s range, even if you feel well — mild anemia with no symptoms still has a cause, and finding it early is the point of the test. Do the same for a high result that stays high on a repeat test.

Seek medical care promptly if a low hemoglobin comes with chest pain, severe breathlessness at rest, fainting, a racing heartbeat that will not settle, confusion, or signs of bleeding such as black tarry stools or vomiting blood — these can signal severe anemia or active blood loss. In pregnancy, any anemia result should be reviewed at your next antenatal visit at the latest, and sooner if you feel unwell. Children with a hemoglobin in the severe band (below 7.0 g/dL under age 5) need same-day assessment.

The bottom line

Read your hemoglobin against three things: the reference range printed on your own report, your age and sex group in the chart above, and, if it is low, the WHO severity bands. Most adults sit between 12.0 and 15.5 g/dL (women) or 13.5 and 17.5 g/dL (men); anemia begins below 12.0 g/dL in women and 13.0 g/dL in men by WHO criteria, and below 10.5 to 11.0 g/dL in pregnancy depending on the trimester. A result outside the range is a starting point for questions — about iron, bleeding, altitude, smoking and hydration first — not a diagnosis on its own.

This article is general information only and is not medical advice. Hemoglobin results should be interpreted by a qualified clinician in the context of your health, your medicines and your other test results. It does not replace professional diagnosis or treatment.