Introduction: Alpha-thalassemia is a genetic disorders that have high prevalence in the human population around all over the world especially in plasmodium falciparum endemic area, characterised by microcytic and hypochromic anaemia. The carriers for the disease present with a mild anaemia can be missed diagnosed as iron deficiency anemia and the patients could take the iron therapy without response. Aim: This a cross sectional hospital base study aimed to find out a guide line to discriminate the high risk patient for alpha thalassemia in Sudan, based on the basic hematological investigation. Methods: Based on the FBC of 98 blood samples of highly suspected patient to alpha thalassemia out of 300 patients with undefined microcytosis were selected for Hb electrophoresis, ferritin and PCR. Results: Of the 98 patients 7 were carriers for the 3.7 deletion mutation which is the most prevalent mutation in African. In these carriers the RBCs and HCT were significantly increased “P-value <0.05”. The Hb level revealed mild decrease without statistical significance “P-value ˃0.05”. The MCV and MCH were clearly decreased, but the MCHC slightly decreased. The Ferritin level was normal and the RDW_CV clearly increased. The quantitative Hb electrophoresis was normal in addition to the presence of many target cells in peripheral picture and no one of these carriers presence with clinical manifestations indicating for anemia. Conclusion: Any patient present with undefined microcytosis, increased RBCs, HCT, RDW_CV with normal Ferritin level, Hb A2 and target cells in peripheral blood should undergo PCR for the 3.7 Alpha deletion mutation.