Aims and method To review the current clinical practice and guidelines for testing and treating vitamin D deficiency in adolescents admitted to a tier 4 adolescent psychiatric unit in north London. The blood test results of 56 patients admitted between 2012 and 2014 were examined to determine whether vitamin D levels had been tested. For those individuals who were tested for vitamin D, results were analysed by gender and ethnicity. Results Of 56 patients admitted, 48% were tested for vitamin D deficiency and in 81.5% of cases we uncovered deficiency or severe deficiency; 18.5% had the minimum levels of vitamin D for bone health as per our trust guidelines. Clinical implications Adolescents within tier 4 adolescent mental health services may be at higher risk of vitamin D deficiency and so assessment of vitamin D levels should be considered as part of a standard physical health review for this group of young people.