Abstract: Methods and apparatuses of the present disclosure provide accurate and precise radiation dosimetry based on decarboxylation of a reactant upon exposure to ionizing radiation. The decarboxylation reaction yields carbon dioxide and stable end products, which can be detected and measured, and correlated to determine an amount of radiation exposure. The reactants include carboxyl acids, such as amino acids and others occurring naturally in mammals. The dosimetry may be performed in real-time or retrospectively by assaying a sample of tissue from a patient. Also disclosed is a device which detects and measures radiation dosages based on decarboxylation of a reactant contained therein.