Characteristics of included studies
| Author | Year | Country | Sample size | N (metformin/ control) | Design | Age | Stroke type | Outcomes |
| Horsdal et al | 2012 | Denmark | 3841 | 563/3278 | PCS | MET+: 71.2 (63–79) | Ischaemic stroke | 30 days, 1 year |
| Kuwashiro et al | 2012 | Japan | 241 | 19/222 | RCS | 71±10 | Ischaemic stroke | 3 months |
| Mima et al | 2016 | Japan | 355 | 77/278 | RCS | 70.1±10.6 | Ischaemic stroke | Discharge |
| Wu et al | 2016 | Multiple | 374 | 148/226 | RCS | 68 (60–76) | ICH | 90 days |
| Westphal et al | 2020 | European | 1919 | 757/1162 | RCS | MET+: 71, MET−: 74 | Ischaemic stroke | 3 months |
| Tu et al | 2021 | China | 730 | 281/449 | RCS | 65 (56–72) | ICH | Discharge, 1 year |
| Akhtar et al | 2022 | Qatar | 2157 | 1132/1025 | RCS | 54.5±13.1 | Ischaemic stroke | Discharge, 90 days |
| Curro et al | 2022 | Italy | 139 | 69/70 | PCS | NR | Ischaemic stroke | 3 months |
| Kersten et al | 2022 | Netherlands | 937 | 592/345 | RCS | MET+: 75 (10), MET−: 76 (11) | Ischaemic stroke | 3 months |
| Tu et al | 2022 | China | 7587 | 3593/3994 | PCS | 66 (57–73) | Stroke | Discharge, 1 year |
| Akiyama et al | 2023 | Japan | 160 | 55/105 | RCS | MET+: 75, MET−: 73 | Ischaemic stroke | Discharge |
| Jian et al | 2023 | China | 224 | 94/130 | RCS | MET+: 64 (54–71), MET−: 65 (56–74) | Ischaemic stroke | 90 days |
NR, not reported; PCS, prospective cohort study; RCS, retrospective cohort study.