Coadministration of multiple dose of metformin (850 mg once daily followed by 500 mg twice daily and 500 mg once daily) was studied with bictegravir/emtricitabine/tenofovir alafenamide (50/200/25 mg once daily) in 32 subjects. Coadministration increased metformin Cmax and AUC by 28% and 39% due to inhibition of renal OCT2 and MATE1 transporters by bictegravir. The pharmacodynamic characteristics of metformin (including glucose reduction, increases in active GLP-1 and plasma lactate) were not affected by coadministration with bictegravir, emtricitabine and tenofovir alafenamide relative to placebo. In addition, no significant differences were observed in fasted blood glucose or HbA1c values before and after initiating bictegravir in HIV+ people with either normal or mildly impaired renal function receiving metformin at daily doses of 500-3000 mg. The US product label for Biktarvy refers to the Prescribing Information of metformin for assessing the benefit and risk of concomitant use of Biktarvy and metformin. This is particularly important in patients with renal impairment. The European product label for Biktarvy indicates that no dose adjustment is required upon coadministration in patients with normal renal function, but for patients with moderate renal impairment, close monitoring should be considered when starting coadministration of bictegravir with metformin, due to increased risk for lactic acidosis in these patients and a dose adjustment of metformin should be considered if required.