The current study was conducted in Najaf Province for the period from the beginning of September 2020 to the end of May 2021 to investigate the parasite Giardia lamblia Among the patients admitted to hospitals and health centers located in Najaf Province, a questionnaire was prepared for each patient to study the factors that may affect the prevalence of infection such as age, gender, treatment of injury, place of residence and occupation. The study included the collection of 350 stool samples from people with diarrhea, whose ages ranged from less than five years to 68 years, and a microscope was used to detect parasites. The results of the current study showed that the number of samples infected with intestinal parasites was 163, with a rate of 46.57%. The percentage of noninfected people was 187, or 53.43%, and it appeared that the symptoms were caused by other factors. The results of the extraction of 57 positive stool samples for patients, whose microscopic examination showed the presence of a parasite In Giardia lamblia, 40 samples of them contained the genetic material of the parasite DNA at a rate of 41%. The results of the PCR examination that were statistically analyzed showed that there were significant differences at the probability level of P < 0.05, as the highest percentage of infection with genotype (B) compared to genotype (A) which amounted to 61.54% and 38.46%, respectively. The current study showed that the amount of heat shock protein HSP70 by using the (ELIZA) test in infected persons and comparing them with healthy samples resulted in an increase in the concentration of HSP70 protein in the serum of persons infected with Giardia lamblia compared with the percentage of its presence in the control group with a significant difference of 0.01