A case has been described suggesting the concomitant use of anabolic androgen steroids as a possible cause of virological failure with long acting cabotegravir/rilpivirine. A 27-year-old MSM had achieved a good virological and immunological response while taking oral antiretroviral therapy for ~10 years and opted to switch to long acting cabotegravir/rilpivirine due to a preference for bi-monthly injections over daily oral intake. Viral load remained undetectable 3 months following the switch. However, 7-8 months after the switch, viral load increased to 635 copies/ml, confirmed 2 weeks later with a level of 814 copies/ml. Resistance testing on the latter sample identified mutations for CAB (N155S) and RPV (E138K); the HIV-1 was subtyped as A6. Plasma trough concentrations of cabotegravir and rilpivirine were notably low: 0.91 mg/L (median population value: 1.6 mg/L; Q1 target: 1.1 mg/L) and 0.026 mg/L (median population value: 0.066 mg/L; Q1 target: 0.032 mg/L), respectively. Apart from multivitamins and occasional diclofenac, his only other medications were anabolic androgen steroids (nandrolone/trenbolone) and testosterone, consistent with his activity in bodybuilding. His physique was muscular with a BMI of 35 kg/m2 ). LA CAB/RPV injections had always been administered on the scheduled target dates. Despite his relatively high BMI, longer needles were not used as intramuscular administration was not problematic and he only had minimal subcutaneous adipose tissue. He was switched to oral boosted protease inhibitor-based ART and regained virological suppression. The authors hypothesize that in this person with HIV and the unfavorable A6 subtype, the concomitant use of anabolic androgen steroids, along with testosterone, may have increased the clearance of cabotegravir and rilpivirine, leading to low trough levels, inadequate virological suppression and the development of two-class resistance.