In vivo (intravascular) hemolysis is relatively rare (1:10 000/100 000) but a life-threatening condition that, among other things, can be caused by parenteral administration of drugs. Potential complications include jaundice, hepatosplenomegaly, tachycardia, myocardial ischemia, renal failure and respiratory failure, and ultimately, multiorgan failure and death. Mortality can be as high as 10 %. Therefore, it is important to assess the hemolytic potential of drugs during the preclinical phase of drug testing. The aim of this study was to establish a simple method for estimating the percentage of hemolysis. Blood samples were treated with saponin, triton-X-100 and propylene glycol to induce hemolysis. The hemoglobin concentrations were determined by the Drabkin reagent method on two types of analyzers: a spectrophotometer with cuwette (Cecil-CE 1011) and an automatic microtiter plate reader (PerkinElmer-VICTOR3 1420 multilabel Counter). The percentage of hemolysis was calculated by dividing the absorbance of treated blood samples with the absorbance of whole blood samples. The method is practical and easy to apply, but it is not suitable for analysis of a large number of samples because it is time consuming and requires precise pipetting. This can be partially improved by using automatic microtiter plate reader that allows simultaneous analysis of multiple samples. Another disadvantage is toxicity of the Drabkin reagent and harmfulness to the environment. The advantage of the method is cheap reagent and existence of the international standard.