Normal Hemoglobin Values
Normal hemoglobin is ≥13.5 g/dL in adult males and ≥12.0 g/dL in adult females, with values below these thresholds defining anemia. 1
Adult Reference Ranges
Males
- Normal threshold: ≥13.5 g/dL
- Anemia is diagnosed at hemoglobin <13.5 g/dL 1
- Mean hemoglobin in healthy adult males (ages 20-59): approximately 150-154 g/dL 1
- 5th percentile ranges from 132-140 g/dL depending on age 1
Females
- Normal threshold: ≥12.0 g/dL
- Anemia is diagnosed at hemoglobin <12.0 g/dL 1
- Mean hemoglobin in healthy adult females (ages 20-59): approximately 124-130 g/dL 1
- 5th percentile ranges from 110-116 g/dL depending on age 1
Important note: The female threshold of 12.0 g/dL reflects exclusion of iron deficiency, as the guidelines adjusted upward from WHO criteria to account for iron-replete women 1
Pediatric Reference Ranges
Hemoglobin varies substantially with age in children 1:
- Ages 1-2 years: Mean 120 g/dL (5th percentile: 107-111 g/dL)
- Ages 3-5 years: Mean 123-124 g/dL (5th percentile: 111-115 g/dL)
- Ages 6-8 years: Mean 129 g/dL (5th percentile: 115-119 g/dL)
- Ages 9-11 years: Mean 133 g/dL (5th percentile: 120-123 g/dL)
- Ages 12-14 years: Mean 141 g/dL in males, 125 g/dL in females (5th percentile: 124-127 g/dL males, 113-121 g/dL females)
- Ages 15-19 years: Mean 151 g/dL in males, 123 g/dL in females 1
The sex-based divergence begins around age 12-14 years, corresponding to puberty 1
Critical Modifying Factors
Altitude
Hemoglobin increases approximately 0.9 g/dL in men and 0.6 g/dL in women per 1,000 meters above sea level 1. The anemia threshold must be adjusted upward accordingly:
| Altitude (meters) | Hemoglobin Adjustment |
|---|---|
| <1,000 | 0 g/dL |
| 1,000 | +0.2 g/dL |
| 1,500 | +0.5 g/dL |
| 2,000 | +0.8 g/dL |
| 2,500 | +1.3 g/dL |
| 3,000 | +1.9 g/dL |
| 4,000 | +3.5 g/dL [1] |
Pregnancy
During pregnancy, hemoglobin thresholds for anemia are lower due to physiologic hemodilution 1:
| Trimester | Anemia Threshold |
|---|---|
| First | <11.0 g/dL |
| Second | <10.5 g/dL |
| Third | <11.0 g/dL [1] |
Smoking
Smokers have elevated hemoglobin due to chronic hypoxia 1:
- All smokers: +0.3 g/dL
- 0.5-1 pack/day: +0.3 g/dL
- 1-2 packs/day: +0.5 g/dL
2 packs/day: +0.7 g/dL 1
Common Pitfalls
Do not adjust hemoglobin thresholds downward for age in males. Although the 5th percentile declines in men over 60 years, this reflects underlying pathology rather than normal aging 1. Anemia in elderly patients warrants investigation, as it associates with increased mortality, hospitalization, cognitive impairment, and cardiovascular disease 1.
In females, hemoglobin remains stable from ages 20-80 years when iron-replete, so no age adjustment is needed 1.
Race-based differences exist (African-Americans have hemoglobin 0.5-0.9 g/dL lower), but the guidelines do not recommend race-specific adjustments for defining anemia 1.