Hemoglobin
Protein in red blood cells that carries oxygen throughout the body
21 of 22 providers
Complete Blood Count (CBC)
Men:13.5-17.5 g/dL, Women:12.0-15.5 g/dL
What is Hemoglobin?
Hemoglobin (Hgb or Hb) is the iron-containing protein in red blood cells responsible for transporting oxygen from your lungs to tissues and carbon dioxide back to lungs for exhalation. Each red blood cell contains about 270 million hemoglobin molecules. Normal hemoglobin levels are 13.5-17.5 g/dL in men and 12.0-15.5 g/dL in women.
Hemoglobin consists of four protein subunits (globin chains) each containing a heme group with an iron atom that binds oxygen. The hemoglobin molecule can carry four oxygen molecules simultaneously. Hemoglobin concentration is the primary criterion for diagnosing anemia (low hemoglobin) and polycythemia (high hemoglobin). Unlike RBC count which measures cell numbers, hemoglobin directly reflects oxygen-carrying capacity.
Hemoglobin is produced in bone marrow and requires iron, vitamin B12, folate, and protein. Each hemoglobin molecule lives 120 days within the RBC. Low hemoglobin causes fatigue, shortness of breath, and reduced exercise tolerance due to inadequate oxygen delivery. High hemoglobin increases blood viscosity and thrombosis risk. Hemoglobin is the single most important parameter from a CBC for assessing overall health and oxygen delivery.
Why Hemoglobin Is the Gold Standard for Oxygen Status
- Defines anemia:WHO criteria—hemoglobin <13 g/dL (men) or <12 g/dL (women) regardless of RBC count or hematocrit
- Oxygen delivery:Directly reflects blood's oxygen-carrying capacity. Each 1 g/dL drop reduces oxygen delivery by ~7%
- Transfusion decisions:Hemoglobin <7-8 g/dL typically requires blood transfusion, especially if symptomatic
- Surgical risk:Low hemoglobin increases perioperative morbidity and mortality. Often corrected before elective surgery
- Athletic performance:Hemoglobin 14-16 g/dL optimal for endurance athletes. Lower levels impair VO2 max and performance
- Cardiovascular stress:Low hemoglobin forces heart to work harder (increased cardiac output), worsening heart failure and ischemia
Optimal vs Standard Ranges
OptimalMen:14.5-16.5 g/dL, Women:13.0-15.0 g/dL▼
- Ideal range for oxygen delivery, energy levels, and cardiovascular health
- Athletes often target upper end of this range
- Provides adequate oxygen for peak physical and cognitive performance without excessive blood viscosity
Borderline LowMen:12.0-14.5 g/dL, Women:11.0-13.0 g/dL▼
- Mild anemia or iron deficiency
- May cause fatigue, reduced exercise capacity
- Check ferritin, iron studies, B12, folate
- Treat underlying cause
- Athletes with hemoglobin in this range will have impaired performance
Moderate Anemia8.0-12.0 g/dL▼
- Moderate anemia causing symptoms (fatigue, dyspnea, tachycardia)
- Requires investigation and treatment
- Check MCV, iron studies, B12, folate, reticulocyte count
- Transfusion generally not needed unless symptomatic or actively bleeding
- Treat underlying cause aggressively
Severe Anemia or Polycythemia<8.0 g/dL or >18.0 g/dL▼
- <8 g/dL:Severe anemia
- Transfusion typically indicated, especially if symptomatic, unstable, or bleeding
- Urgent investigation for cause
- >18 g/dL:Severe polycythemia
- High thrombosis risk
- Urgent phlebotomy and investigation for polycythemia vera or secondary causes
Scientific Evidence
WHO Anemia Definitions
World Health Organization defines anemia as hemoglobin <13 g/dL in men, <12 g/dL in non-pregnant women, and <11 g/dL in pregnant women. These thresholds are based on population distributions and associated with increased morbidity, reduced quality of life, and impaired physical/cognitive function. Anemia affects 1.6 billion people worldwide.
Transfusion Thresholds
Restrictive transfusion strategy (transfuse only if hemoglobin <7 g/dL in stable patients) is as safe as liberal strategy (transfuse at <10 g/dL) and reduces blood usage by 40%. Exception:acute coronary syndrome patients benefit from hemoglobin >8 g/dL. These findings changed transfusion practice worldwide.
Iron Deficiency Anemia Treatment
Oral iron therapy (ferrous sulfate 200 mg 2-3 times daily) increases hemoglobin by 1-2 g/dL per month in iron deficiency anemia. IV iron produces faster response (2-4 weeks) and is superior when oral iron fails, malabsorption exists, or rapid repletion needed. Hemoglobin >12 g/dL is achieved in 90% of patients by 3 months.
ESA Target Hemoglobin in CKD
In chronic kidney disease patients on dialysis, targeting higher hemoglobin (13-15 g/dL) with ESAs increases stroke and cardiovascular events compared to targeting 10-11 g/dL, without improving quality of life. Current guidelines recommend ESA use only if hemoglobin <10 g/dL, targeting 10-11 g/dL to avoid cardiovascular risks.
Source:KDOQI. Clinical Practice Guideline for Anemia in Chronic Kidney Disease. Am J Kidney Dis. 2012;60(5):850-886.
Hemoglobin and Athletic Performance
Hemoglobin directly correlates with VO2 max (maximal oxygen uptake) and endurance performance. Each 1 g/dL increase in hemoglobin improves VO2 max by ~4% in endurance athletes. This explains the performance advantage of altitude training (increases hemoglobin) and the use (and banning) of EPO doping in competitive sports.
Source:Calbet JA, et al. Importance of hemoglobin concentration to exercise:acute manipulations. Respir Physiol Neurobiol. 2006;151(2-3):132-140.
Which Providers Test Hemoglobin?
Full Provider Comparison
| Provider | Includes | Annual Cost | Biomarkers |
|---|---|---|---|
 Superpower | ✓ | $199 | 100+ (150 with ratios) |
 WHOOP Advanced Labs | ✓ | $349 | 65 |
 Labcorp OnDemand | ✓ | $398 | 30+ |
| ✓ | $486 | 40+ | |
| ✓ | $444 | 288 | |
| ✓ | $349 | 100+ | |
| ✓ | $761 | 54 | |
 Function Health | ✓ | $365 | 160+ |
| ✓ | $250 | 65 | |
| ✓ | $495 | 70+ | |
| ✓ | $895 | 100+ | |
| ✓ | $1950 | 150+ | |
| ✓ | $375 | 80+ | |
| — | $Varies | 75+ | |
| ✓ | $190 | 100+ | |
| ✓ | $99 | 50 | |
| ✓ | $124 | 60 | |
| ✓ | $199 | 50 | |
| ✓ | $499 | 120+ | |
| ✓ | $4188 | 70-80+ | |
| ✓ | $375 | 85 | |
| ✓ | $700 | 128 |
Frequently Asked Questions
What is Hemoglobin?
Protein in red blood cells that carries oxygen throughout the body
What is the optimal range for Hemoglobin?
The standard reference range for Hemoglobin is Men:13.5-17.5 g/dL, Women:12.0-15.5 g/dL. Optimal ranges may differ based on individual health goals and expert recommendations.
Which blood test providers include Hemoglobin?
21 out of 22 blood testing providers include Hemoglobin in their panels. This biomarker is widely available across major providers.
What category does Hemoglobin fall under?
Hemoglobin is categorized under Complete Blood Count (CBC). This category includes biomarkers that help assess related aspects of health and wellness.
Medical Disclaimer
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider about your specific health needs.
Last reviewed:2026-02-20