. 2018 Sep 3;11(1):7–14. doi: 10.1093/inthealth/ihy060

Table 1.

G6PD genotypes and associated phenotypes. The g6pd gene lies on the X chromosome. Males have only one allele, encoding either a G6PD enzyme with deficient activity (Def.) or normal activity (Norm.). Females have two alleles so they can have either two identical alleles (homozygous) or two different alleles (heterozygous). The associated phenotypes are described in the right two columns

Genotype				Phenotype
Male		Female		Category	% Normal activity^a
Type	Allele	Type	Allele	Category	% Normal activity^a
Hemizygous	Def.	Homozygous	Def.₁ Def.₁	Severe deficient	<30%
Hemizygous	Def.	Heterozygous	Def.₁ Def.₂	Severe deficient	<30%
		Heterozygous	Def. Norm.	Intermediate or mildly deficient	Mostly between 30% and 80%^b
Hemizygous	Norm.	Heterozygous	Norm.₁ Norm.₂	Normal	>80%
Hemizygous	Norm.	Homozygous	Norm.₁ Norm.₁	Normal	>80%

^aNormal activity or 100% can be defined as the median activity of male hemizygous normal.

^bHeterozygous females can range from severely deficient G6PD levels to normal, but lie mostly within the 30–80% activity range.