The aim of this study was to determine 25-hydroxy vitamin D3 levels in diarrhoeic goat kids. For this purpose, blood sample witdrawn from 10 diarrhoeic goat kids (Group I) and 10 healthy goat kids (Group II). Diagnosis of giardiasis was performed with multiple methods including microscopic examination and rapid test kits. Mean 25-hydroxy vitamin D3 levels were determined as 33,37 ng/ml in diarrhoetic goat kids and 86,78 ng/ml in control and that is found to statistically significant (p<0.001). Consequently, it was convinced that giardiasis-related intestinal malabsorption may cause severe reduction in vitamin D levels and vitamin D supplement should be administered proper and sufficient doses due to anti-microbial effect with anti-giardial medication in treatment regime.