Normal hemoglobin levels fall between 14 and 18 g/dL for men and 12 to 16 g/dL for women. These ranges reflect the amount of the oxygen-carrying protein packed into your red blood cells, and they shift based on age, pregnancy, altitude, and even whether you smoke.
What Hemoglobin Does
Hemoglobin is the protein inside red blood cells responsible for picking up oxygen in your lungs and delivering it to every tissue in your body. Each hemoglobin molecule can carry up to four oxygen molecules at once, bound to iron atoms at its core. When your hemoglobin drops too low, your tissues don’t get enough oxygen. When it climbs too high, your blood thickens and flows less efficiently. Either direction causes problems, which is why the number matters.
Normal Ranges for Adults
The standard reference ranges most labs use are straightforward:
- Men: 14 to 18 g/dL
- Women: 12 to 16 g/dL
The difference between men and women comes down to testosterone, which stimulates red blood cell production. After menopause, women’s levels tend to rise slightly but generally stay within the same reference range.
Normal Ranges for Children
Children’s hemoglobin levels change dramatically in the first year of life, then gradually climb toward adult values. Newborns start high, with an average around 16.5 g/dL, because they needed extra oxygen-carrying capacity in the womb. By two months, that average drops to about 11.2 g/dL as the body breaks down the excess fetal red blood cells. This dip is normal and not a sign of anemia.
From six months to age two, the average sits around 12 g/dL, with anything below 10.5 g/dL considered anemic. School-age children (6 to 12 years) average about 13.5 g/dL, and the lower threshold for concern is 11.5 g/dL. By the teen years, boys and girls begin to diverge: boys average 14.5 g/dL while girls average 14 g/dL, and the gap widens through adulthood.
Hemoglobin During Pregnancy
Pregnancy naturally lowers hemoglobin because your blood volume expands by nearly 50%, diluting the red blood cells you have. The thresholds for anemia in pregnancy are lower than usual to account for this:
- First trimester: below 11 g/dL
- Second trimester: below 10.5 g/dL
- Third trimester: below 11 g/dL
The second trimester cutoff is the lowest because that’s when blood volume peaks relative to red blood cell production. A reading of 10.8 g/dL at 24 weeks, for example, would be within the expected range for pregnancy even though it would flag as mildly anemic outside of it.
How Anemia Severity Is Graded
Not all low hemoglobin is equally serious. The World Health Organization classifies anemia into three tiers, and the cutoffs differ slightly by group:
For men, mild anemia falls between 11 and 12.9 g/dL, moderate between 8 and 10.9 g/dL, and severe below 8 g/dL. For non-pregnant women, the mild range is narrower: 11 to 11.9 g/dL, with moderate and severe matching the same thresholds. Pregnant women have their own scale, where mild is 10 to 10.9 g/dL, moderate is 7 to 9.9 g/dL, and severe falls below 7 g/dL.
Mild anemia often produces no obvious symptoms or just subtle fatigue. Moderate anemia typically brings noticeable weakness, dizziness, and cold hands and feet. Severe anemia can cause shortness of breath at rest, a racing heartbeat, and dangerous drops in oxygen delivery to your organs.
When Hemoglobin Is Too High
High hemoglobin gets less attention than low, but it carries its own risks. Levels above 16.5 g/dL in men or 16 g/dL in women raise suspicion for polycythemia, a condition where the body produces too many red blood cells. The blood becomes thicker, which increases the risk of clots, stroke, and heart attack.
Not every elevated reading means disease, though. Two common, non-threatening causes push hemoglobin above those thresholds: altitude and smoking.
Altitude and Smoking Adjustments
If you live at high altitude, your body compensates for thinner air by producing more hemoglobin. The WHO recommends adding to the standard cutoffs when screening people at elevation, ranging from an extra 0.2 g/dL at 1,000 meters (about 3,300 feet) up to 4.5 g/dL at 4,500 meters (roughly 14,800 feet). A 2025 study of Colombian populations found that a significant proportion of people living above 2,000 meters exceeded standard polycythemia cutoffs without any clinical signs of disease, reinforcing that altitude-adjusted ranges are important for accurate diagnosis.
Smoking also raises hemoglobin, and for a less beneficial reason. Carbon monoxide from cigarette smoke binds to hemoglobin and forms an inactive version that can’t carry oxygen. Your body responds by ramping up hemoglobin production to compensate for the lost capacity. Studies consistently show that smokers carry significantly higher hemoglobin levels than non-smokers regardless of sex. This means a smoker with a hemoglobin of 17 g/dL may actually have less functional oxygen-carrying ability than a non-smoker at 15 g/dL. Some labs apply a correction factor, subtracting about 0.3 to 0.5 g/dL for light smokers and more for heavy smokers, to get a truer picture.
What Affects Your Results
Beyond altitude and smoking, several everyday factors can shift your hemoglobin reading. Dehydration concentrates your blood and can temporarily push hemoglobin higher than your true baseline. Overhydration or having blood drawn while you’re lying down can dilute it slightly. Iron intake, vitamin B12, and folate all influence how effectively your body builds hemoglobin, so deficiencies in any of these show up as lower numbers over time.
Endurance athletes sometimes have lower hemoglobin than expected because intense training expands blood plasma volume, a phenomenon called sports anemia. It’s usually not true anemia and doesn’t impair performance. Chronic kidney disease, on the other hand, reduces production of the hormone that signals your bone marrow to make red blood cells, leading to a genuine and often significant drop in hemoglobin.
Because so many variables influence the number, a single hemoglobin reading is a starting point, not a diagnosis. The trend over multiple tests, combined with how you feel, gives a much clearer picture than any isolated value.