Introduction: The risk of vitamin D toxicity is tremendously increased due to erroneous prescriptions along with prolonged and overconsumption of vitamin supplementation.

Aim: This study aimed to assess the histopathological changes caused by vitamin D3 overdose on albino rats' tongue.

Material & Methods: Twenty adult male Wister rats were randomly divided into two groups (n=10): control group and experimental vitamin D3 overdose treated group (200 IU of vitamin D3) (1 ml/kg/day Cholecalciferol) for 30 days through oral gavage. Rat tongue was processed for histopathological assessment using routine hematoxylin and eosin and Alizarin red along with immunohistochemical assessment of TNF-α.

Results: Histological examination revealed loss of some filiform papillae of mucosal tongue epithelium, pyknotic nuclei of some cells of its basal layer, focal loss with rarefaction of cytoplasm of certain striated muscle fibers. Increased TNF-α immunoexpression has been detected along with increased calcification as revealed by alizarin red staining compared with controls.

Conclusion: Vitamin D3 overdose in rats was associated with histological and immunohistochemical changes in the tongue tissues so vitamin D must be taken under medical supervision.