Kenya has made positive progress towards achieving Millennium Development Goals and Vision 2030; however, HIV and AIDS
remains a major challenge, causing premature mortality and morbidity and unless its impacts are controlled the country may not
achieve its development goals. Antiretroviral therapy is one of the response mechanisms that are being implemented globally to
mitigate the impact of HIV. The objectives of this study was to estimate the unit costs of labour, laboratory and imaging services,
average cost per inpatient day and the average cost of outpatient visit per quarter in Mbagathi District Hospital. The cost and
health service utilization data was collected retrospectively for a period of 24 months from the electronic medical records and
patient charts of 351 HIV-positive adults who were enrolled on ART treatment in Mbagathi. Using micro-costing and grosscosting
methods, we estimated the economic cost of the comprehensive HIV treatment. The average cost of outpatient visit per
quarter was estimated to be Ksh9,044 (USD120.83)during the three months of treatment debut. This decreased over the two
years of follow-up to Ksh5,818 (USD77.73) while the average cost per outpatient visit stood at Ksh2,001 (USD26.73). The
average outpatient cost per annum was Ksh26,040 (USD347.90)and Ksh20,506 (USD273.96) in the first and the second year of
treatment, respectively. The average cost of treatment per inpatient day was Ksh1,691 (USD22.59). The average labour cost per
outpatient visit was Ksh465 (USD6.21) while that of inpatient per day was Ksh575 (USD7.68). Generally, ART accounted for the
highest proportion of costs followed by the labour and laboratory test. The study provides new and relevant information in terms
of the unit costs of inpatient and outpatient care, labour, laboratory and imaging.