Hypertension is a major modifiable cardiovascular risk factor that is affecting more individuals globally. In addition to poor treatment adherence, genetic diversity may be linked to pharmacological efficacy. In family genetics, heritability of blood pressure ranges from 30% to 50%. Antihypertensive treatment response is genetically variable. Candesartan is frequently utilized as a first-line therapy for hypertension patients, regardless of therapeutic efficacy, which reveals interindividual variability in hypertensive patients. It depends on the ABO gene polymorphism and blood group. Angiotensin II (ACE) elevates blood pressure. In the Kerbala'a province, we look into ACE activity and candesartan responsiveness. The study comprised 92 hypertension patients taking 8 mg candesartan once day. ACE, angiotensin II, blood type, blood pressure, and heart rate were all tested. The genetic variant ABO (T>G) rs495828 strongly affects ACE levels in hypertensive patients. For patients with high ACE and angiotensin II levels, candesartan is a viable choice, but it is not for those with low levels.