G6PD Activity of 450 U/g Hemoglobin: Normal Result
A G6PD activity of 450 U/g hemoglobin is well above normal reference ranges and indicates no G6PD deficiency—you can safely prescribe oxidative drugs including primaquine, dapsone, sulfonamides, nitrofurantoin, and high-dose vitamin C without risk of drug-induced hemolysis. 1
Understanding Your Result
Your G6PD level of 450 U/g Hb is substantially elevated compared to typical normal ranges:
- Normal median G6PD activity ranges from approximately 6.3–15.6 U/g Hb depending on the assay platform used 2
- Your result of 450 U/g Hb is roughly 30–70 times higher than typical normal values, which suggests either a reporting error (perhaps the units are different, such as U/L rather than U/g Hb) or an extremely elevated reticulocyte count 1, 2
Critical interpretation point: Calculate your percentage of normal activity by dividing your result by the laboratory's upper limit of normal and multiplying by 100. 1 If your laboratory's upper limit is, for example, 15 U/g Hb, your percentage would be (450/15) × 100 = 3000%, which is physiologically implausible for a stable G6PD measurement.
Medication Safety Based on G6PD Thresholds
Regardless of the absolute number, the key clinical thresholds are: 1, 3
- <30% of normal activity = severe deficiency; all oxidant drugs absolutely contraindicated 1, 3
- 30–70% of normal activity = intermediate deficiency; modified primaquine dosing possible for non-Mediterranean variants with close monitoring 1, 3
- >70% of normal activity = safe for tafenoquine and standard-dose oxidant drugs 1, 4
Your result clearly exceeds 70% of normal activity, placing you in the safe category for all oxidant medications. 1
Absolutely Safe Medications at Your G6PD Level
The following drugs are definitively contraindicated only in G6PD deficiency (<30% activity), and are safe at your level: 3, 5
- Primaquine (for malaria radical cure) 3, 5
- Tafenoquine (requires >70% activity; you qualify) 1, 4
- Dapsone (for dermatologic conditions and Pneumocystis prophylaxis) 3, 5
- Methylene blue (methylthioninium chloride) 3, 5
- Rasburicase (for tumor lysis syndrome) 3, 5
- Nitrofurantoin (for urinary tract infections) 5
- Sulfonamides (various antibacterial indications) 1
Common Pitfalls to Avoid
Verify the units of measurement with your laboratory. 1, 4 The most common reporting unit is U/g hemoglobin, but some laboratories report in U/L of red blood cells, U/10¹² red cells, or other formats. A result of "450" in U/L would still be normal (typical range 4.6–13.5 U/g Hb converts to roughly 140–400 U/L), but the interpretation changes dramatically based on units. 4, 2
Do not retest during acute illness or hemolysis. 1 Reticulocytes and young red cells contain near-normal G6PD levels even in deficient individuals, which can mask true deficiency. Your current result, if obtained during a stable baseline state, is reliable. 1
Transfusion history matters. 1 If you received red cell transfusions within the past 50–120 days, donor cells (even 6–12% contamination) can falsely elevate your measured activity. 1
No Dietary or Lifestyle Restrictions Required
With normal G6PD activity, you have no need to avoid: 3, 6
- Fava beans (the classic trigger in Mediterranean-variant G6PD deficiency)
- High-dose vitamin C supplementation
- Naphthalene-containing mothballs
- Henna dye exposure
Bottom Line for Clinical Decision-Making
Your G6PD activity of 450 U/g Hb—assuming correct units—indicates you are not G6PD deficient and face no increased risk of drug-induced hemolytic anemia from oxidant medications. 1, 3 Confirm the units with your laboratory to ensure accurate interpretation, but at any plausible unit conversion, this result excludes G6PD deficiency. 4, 2