Cast-in anchors are embedded into concrete substrates to provide sufficient anchorage for both structural and non-structural components. In recent years, the use of higher strength cementitious mixtures (>50 MPa) often with the inclusion of steel fibres have been gaining popularity due to superior mechanical properties and durability. However, current design codification has been developed for normal strength concrete substrates which may lead to overly conservative or even unsafe designs for cast-in anchors in Ultra High-Performance Fibre Reinforced Concrete (UHPFRC). This paper presents an assessment of currently employed design standards and analytical models from the literature. Experimental results from 247 tests have been collated and compared to design predictions. The analysis of the experimental data base focused on the following parameters: concrete mixture type and compressive strength, bearing pressure under anchor heads, and embedment depth. Design predictions significantly underestimate concrete breakout capacity in UHPFRC slabs. In some cases where cast-in fasteners are used in thin slabs, design models were found to be unsafe, with breakout capacity being overestimated by much as 28% due to specimen dimensions having an effect on failure mode. This highlights the inadequacy of current design approaches for high-strength, fibre-reinforced concretes, as they often neglect critical parameters such as anchor and specimen geometry, as well as fibre content.