In 2025, the guideline for the realisation of monitoring of occupational intakes of radionuclides (internal monitoring) in Germany was revised. For this purpose, an expert workgroup was mandated to consider the amended German radiation protection legislation, amended international standards and recommendations as well as other recent developments in the subject area. The methodology of the revised guideline for the calculation of the likely committed effective dose based on the handled activity and incorporation factors adapts international recommendations and standards. However, the definitions and values of the subfactors from which the incorporation factors are calculated deviate from international recommendations, for example the physical form safety factor considers the volume or mass of the handled radioactive material. For applications in nuclear medicine, specific incorporation factors based on recent literature are tabulated. Regarding the monitoring of persons of childbearing potential, an assessment of the equivalent dose for the uterus and if required a monthly monitoring are prescribed. Quality assurance of approved monitoring services is based optionally on accreditation or on audits by public authorities. For workplace monitoring, technical requirements, in particular quality-assurance procedures, are also specified. Regarding the dose assessment, a reference method and several individual methods are described, with the investigation threshold for changing to individual methods corresponding to an effective dose of 6 mSv during the calendar year. For the reference method, standard assumptions (inhalation, AMAD 5 μm for workplaces, 1 μm for emergency workers with environmental exposure) are applied.