What are normal hemoglobin (Hb) levels?

Normal Hemoglobin Levels in Adults

Normal hemoglobin is ≥13.5 g/dL in adult males and ≥12.0 g/dL in adult females, with anemia diagnosed below these thresholds. 1, 2

Sex-Specific Reference Ranges

Adult Males

• Lower limit of normal: 13.5 g/dL 1
• Complete normal range: 13.5-17.5 g/dL 1
• No age adjustment should be made despite declining hemoglobin in older men, as lower values reflect poor health rather than normal aging 1

Adult Females

• Lower limit of normal: 12.0 g/dL 1, 2
• Complete normal range: 12.0-15.5 g/dL 2
• This 12.0 g/dL threshold is preferred over the WHO definition (which uses <12.0 g/dL for women) because it excludes iron-deficient individuals from the reference population, making it more clinically appropriate 2
• Hemoglobin remains stable between ages 20-80 years in women, requiring no age adjustment 1

Critical Modifying Factors

Race/Ethnicity

• African American individuals have hemoglobin levels 0.5-1.0 g/dL lower than Caucasians 2
• The lower limit of normal for Black women can be as low as 9.6 g/dL in some populations 2
• This represents physiologic variation, not pathology 1

Altitude

Hemoglobin increases with altitude exposure and requires upward adjustment of normal thresholds: 1

• <1,000 meters: no adjustment 1
• 1,000 meters: +0.2 g/dL 1, 2
• 1,500 meters: +0.5 g/dL 1, 2
• 2,000 meters: +0.8 g/dL 1, 2
• 2,500 meters: +1.3 g/dL 1, 2
• 3,000 meters: +1.9 g/dL 1, 2

Smoking

• Smoking increases hemoglobin by 0.3-1.0 g/dL and must be considered when interpreting values 2

Clinical Significance of These Thresholds

Values below these thresholds warrant investigation, as even mild anemia (11.0-11.9 g/dL) significantly increases mortality risk. 3 The optimal hemoglobin for survival in older adults is 15.0-15.9 g/dL in men and 13.0-13.9 g/dL in women, with mortality risk increasing substantially below 14 g/dL in men and 12 g/dL in women. 3

Important Caveats

• Iron deficiency can cause symptoms even before hemoglobin drops below the anemia threshold 4
• In premenopausal women, menstrual losses may lower the practical threshold to 11.0 g/dL (representing the 5th percentile) 2
• Pregnancy causes physiologic hemodilution in the first and second trimesters, requiring different reference ranges 1

Special Population: Chronic Kidney Disease

For patients with CKD receiving erythropoiesis-stimulating agent (ESA) therapy, different targets apply: 1, 2

• Target range: 11.0-12.0 g/dL 1, 2
• Never target hemoglobin >13.0 g/dL due to increased cardiovascular mortality risk 1, 2
• Avoid letting hemoglobin fall below 9.0 g/dL in dialysis patients 1