There are various limitations to MTT assays. They are as follows, they are not that sensitive, have chemical interference, and have toxicity. The conversion to formazan crystals depends on the metabolic rate, as well as the quantity of mitochondria, resulting in chemical interference. The reagent is also naturally cytotoxic, and  can kill the cells inadvertently, especially eukaryotic cells. As for the sensitivity, MTT assays are less sensitive at detecting absorption than fluorescent and luminescent techniques for calculating cell viability.