This study showed that Hb Malay with β0-thalassemia, including codon 17 (A>T), codon 41 (− C), codons 41/42 (− TTCT), IVS1-1 (G>T), or β+-thalassemia, including IVS1-5 (G>C) and IVS2-654 (C>T), led to severe anemia, wherein patients required regular blood transfusion. Here, GSTM1 is linked to anemia (phenotype).