Supplementary Data — Metformin reduces COVID-19 risk: real-time meta-analysis of 114 studies

October 2026

Metformin COVID-19 outcomes

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk
Bramante (DB RCT)3%0.97 · 0.06–15.46death1/4081/396COVID-OUTOT1 Bramante (DB RCT)−197%2.97 · 0.12–72.71death1/4080/396COVID-OUTOT1 Bramante (DB RCT)52%0.48 · 0.20–1.11death/hosp.8/65218/655COVID-OUTOT1 Bramante (DB RCT)40%0.60 · 0.37–0.94progression27/65248/655COVID-OUTOT1 Bramante (DB RCT)12%0.88 · 0.73–1.06progression154/652179/653COVID-OUTOT1 Bramante (DB RCT)37%0.63 · 0.48–0.83viral+72/504112/495COVID-OUTOT1 Bramante (DB RCT)9%0.91 · 0.81–1.03viral+251/504270/495COVID-OUTOT1 Bramante53%0.47 · 0.25–0.89PASC10/24821/248 Abu-Jamous65%0.35 · 0.11–0.84death4/2394/168 Tamura97%0.03 · 0.00–0.58death115 (n)73 (n) Li76%0.24 · 0.06–0.98death2/3721/94 Shaseb (RCT)74%0.26 · 0.06–1.06death85 (n)104 (n) Shaseb (RCT)79%0.21 · 0.04–0.99ventilation85 (n)104 (n) Shaseb (RCT)63%0.37 · 0.13–1.09ICU85 (n)104 (n) Shaseb (RCT)5%0.95 · 0.82–1.11hosp. time85 (n)104 (n) Ventura-.. (DB RCT)44%0.56 · 0.33–0.95oxygen time10 (n)10 (n) Ventura-.. (DB RCT)10%0.90 · 0.72–1.12hosp. time10 (n)10 (n) Ventura-.. (DB RCT)41%0.59 · 0.37–0.95viral time10 (n)10 (n) Mehrizi44%0.56 · 0.53–0.60deathpopulation-based cohort Sugimoto40%0.60 · 0.53–0.66deathpopulation-based cohort Sugimoto41%0.59 · 0.51–0.68misc.population-based cohort He74%0.26 · 0.20–0.34death53,030 (all patients) He72%0.28 · 0.19–0.40death53,030 (all patients) He74%0.26 · 0.18–0.39death53,030 (all patients) Bramante (DB RCT)−43%1.43 · 0.32–6.38hosp.4/1,4433/1,548ACTIV-6 Bramante (DB RCT)20%0.80 · 0.41–1.56progression15/1,44320/1,548ACTIV-6 Bramante (DB RCT)−25%1.25 · 0.82–1.78progression54/1,44359/1,548ACTIV-6 Bramante (DB RCT)−8%1.08 · 0.78–1.42progression1,443 (n)1,548 (n)ACTIV-6 Bramante (DB RCT)4%0.96 · 0.57–1.41progression1,443 (n)1,548 (n)ACTIV-6 Bramante (DB RCT)1%0.99 · 0.66–1.31progression1,443 (n)1,548 (n)ACTIV-6 Bramante (DB RCT)−4%1.04 · 0.97–1.12no recov.58/1,44353/1,548ACTIV-6 Bramante (DB RCT)10%0.90 · 0.84–0.97no recov.1,443 (n)1,548 (n)ACTIV-6 Bramante (DB RCT)12%0.88 · 0.80–0.96no recov.1,443 (n)1,548 (n)ACTIV-6 Bramante (DB RCT)21%0.79 · 0.47–1.23PASC1,439 (n)1,544 (n)ACTIV-6 Bramante (DB RCT)27%0.73 · 0.47–1.08PASC1,439 (n)1,544 (n)ACTIV-6 Bramante (DB RCT)8%0.92 · 0.58–1.32PASC1,439 (n)1,544 (n)ACTIV-6 Bramante (DB RCT)50%0.49 · 0.15–0.99PASC1,439 (n)1,544 (n)ACTIV-6 Bramante (DB RCT)12%0.88 · 0.35–1.63PASC1,439 (n)1,544 (n)ACTIV-6 Bramante (DB RCT)14%0.86 · 0.51–1.32PASC1,439 (n)1,544 (n)ACTIV-6 Bramante (DB RCT)35%0.65 · 0.43–0.95PASC1,439 (n)1,544 (n)ACTIV-6 Bramante (DB RCT)10%0.90 · 0.57–1.34PASC1,439 (n)1,544 (n)ACTIV-6 Lin (PSM)33%0.67 · 0.05–9.20death41 (n)41 (n) Lin (PSM)−45%1.45 · 0.47–4.46ventilation41 (n)41 (n) Chaichana62%0.38 · 0.31–0.47PASCpopulation-based cohort Luo75%0.25 · 0.07–0.84death3/10422/179 Cariou20%0.80 · 0.45–1.43death746 (n)571 (n)CORONADO Choi (PSM)−120%2.20 · 0.51–9.58progressioncase-control study Wang58%0.42 · 0.01–1.98death1/913/49 Chen33%0.67 · 0.20–1.78death4/4315/77 Kim64%0.36 · 0.10–1.23death113 (n)122 (n) Kim52%0.48 · 0.19–1.24progression113 (n)122 (n) Li78%0.22 · 0.09–0.54death2/3721/94 Li−27%1.27 · 0.12–13.59ventilation1/372/94 Mirani45%0.55 · 0.27–1.11death25/6913/21 Goodall3%0.97 · 0.75–1.25death74/210280/771 Gao−225%3.25 · 1.03–7.41progression16/564/54 Pérez-Bel.. (PSM)−10%1.10 · 0.84–1.40death79/24979/249 Bramante12%0.88 · 0.78–1.00death394/2,333791/3,923 Bramante21%0.79 · 0.65–0.95death1,129 (n)2,173 (n) Bramante4%0.96 · 0.82–1.14death1,204 (n)1,750 (n) Sourij37%0.63 · 0.33–1.10death14/7744/161 Lalau (PSM)22%0.78 · 0.55–1.10death671 (n)419 (n) Lalau (PSM)18%0.82 · 0.61–1.11death/int.671 (n)419 (n) Lalau (PSM)7%0.93 · 0.64–1.35ventilation671 (n)419 (n) Huh−1%1.01 · 0.81–1.23progression104/272774/2,533 Huh4%0.96 · 0.82–1.12casescase-control study Ramos-Rincón1%0.99 · 0.77–1.29death206/420179/370 Crouse61%0.39 · 0.16–0.87death8/7634/144 Lally52%0.48 · 0.28–0.84death16/127144/648 Oh−26%1.26 · 0.81–1.95death5,946 (n)5,946 (n) Oh (PSM)28%0.72 · 0.63–0.81cases390/5,946541/5,946 Wargny28%0.72 · 0.53–0.95death247/1,553330/1,241CORONADO Wargny15%0.85 · 0.74–0.97no disch.690/1,553702/1,241CORONADO Bramante (PSM)62%0.38 · 0.16–0.91death342 (n)342 (n) Bramante68%0.32 · 0.15–0.66death676 (n)8,879 (n) Bramante (PSM)−9%1.09 · 0.62–1.91ICU342 (n)342 (n) Bramante32%0.68 · 0.45–1.02ICU676 (n)8,879 (n) Bramante22%0.78 · 0.58–1.04hosp.676 (n)8,879 (n) Holt−27%1.27 · 0.72–2.22cases12/429434/14,798COVIDENCE UK Khunti23%0.77 · 0.73–0.81deathpopulation-based cohort Jiang (PSM)46%0.54 · 0.13–2.26death3/7410/74 Jiang (PSM)80%0.20 · 0.05–0.77progression8/7417/74 Ghany66%0.34 · 0.19–0.59death392 (n)747 (n) Ghany29%0.71 · 0.52–0.86hosp.392 (n)747 (n) Ghany68%0.32 · 0.22–0.45ARDS392 (n)747 (n) Alamgir27%0.73 · 0.63–0.84death11,062 (n)11,062 (n) Alamgir34%0.66 · 0.49–0.90death5,369 (n)5,369 (n) Alamgir30%0.70 · 0.53–0.95death2,525 (n)2,525 (n) Gálvez-Barrón−16%1.16 · 0.73–1.49death20 (n)83 (n) Gálvez-Barrón−16%1.16 · 0.73–1.49severe case20 (n)83 (n) Ravindra30%0.70 · 0.28–1.56death5/5357/313 Blanc79%0.21 · 0.03–1.46death1/1425/75 Blanc−44%1.44 · 1.00–2.07cases11/1678/163 Boye10%0.90 · 0.86–0.94hosp.2,067/4,2503,196/5,281 Do−8%1.08 · 0.61–1.89death469 (n)1,301 (n) Do−38%1.38 · 0.97–1.97death469 (n)1,301 (n) Do23%0.77 · 0.44–1.35death469 (n)95 (n) Do−35%1.35 · 0.89–2.06ventilation469 (n)1,301 (n) Do−40%1.40 · 0.86–2.25ventilation469 (n)1,301 (n) Do−20%1.20 · 0.53–3.10ventilation469 (n)95 (n) Cheng (PSM)−65%1.65 · 0.71–3.86death678 (n)535 (n) Wang12%0.88 · 0.81–0.97ICU6,504 (n)10,000 (n) Ando39%0.61 · 0.38–0.99hosp. Wander15%0.85 · 0.80–0.90death Wander2%0.98 · 0.92–1.06ICU Wander3%0.97 · 0.94–1.01hosp. Luk49%0.51 · 0.27–0.97death737 (n)254 (n) Luk49%0.51 · 0.27–0.97ventilation737 (n)254 (n) Luk47%0.53 · 0.33–0.86ICU737 (n)254 (n) Saygili (PSM)42%0.58 · 0.37–0.92death120 (n)120 (n) Ong47%0.53 · 0.31–0.87death33/18657/169 Ong24%0.76 · 0.50–1.10death28/10957/169 Ong85%0.15 · 0.04–0.55death2/4057/169 Ong76%0.24 · 0.07–0.68death3/3757/169 Pazoki−13%1.13 · 0.73–1.74death177 (n)216 (n) Pazoki−24%1.24 · 0.67–2.28severe case177 (n)216 (n) Bliden60%0.40 · 0.12–1.37death3/349/41 Bliden76%0.24 · 0.06–1.03ventilation2/3410/41 Al-Salameh55%0.45 · 0.17–0.94death/ICU9/4722/50 Al-Salameh−68%1.68 · 1.12–2.05death/ICU34/4322/50 Wallace (PSW)72%0.28 · 0.21–0.37death103/1,2031,536/6,970 Ojeda-Fern.. (PSM)16%0.84 · 0.79–0.89death1,476/6,5561,787/6,556 Ojeda-Fern.. (PSM)22%0.78 · 0.72–0.84death968/6,5561,261/6,556 Ojeda-Fern.. (PSM)22%0.78 · 0.64–0.95ICU166/6,556212/6,556 Ojeda-Fern.. (PSM)3%0.97 · 0.94–1.00hosp.3,551/6,5563,670/6,556 Ojeda-Fern.. (PSM)8%0.92 · 0.84–1.00death793/3,297876/3,297 Ojeda-Fern.. (PSM)16%0.84 · 0.75–0.94death512/3,297618/3,297 Ojeda-Fern.. (PSM)39%0.61 · 0.44–0.82ICU64/3,297102/3,297 Ojeda-Fern.. (PSM)−2%1.02 · 0.97–1.07hosp.1,822/3,2971,792/3,297 Fu72%0.28 · 0.09–0.84no recov.4/499/31OT1 Usman60%0.40 · 0.12–1.37death3/349/41 Usman76%0.24 · 0.06–1.03ventilation2/3410/41 Usman34%0.66 · 0.39–1.13hosp. time34 (n)41 (n) Wong51%0.49 · 0.43–0.57death Wong41%0.59 · 0.52–0.66ventilation Wong40%0.60 · 0.57–0.63hosp. Wong (PSW)59%0.41 · 0.22–0.80death786 (n)428 (n) Wong (PSW)61%0.39 · 0.21–0.75no recov.786 (n)428 (n) Wong (PSW)64%0.36 · 0.18–0.76improv.786 (n)428 (n) Wong (PSW)56%0.44 · 0.24–0.81no disch.786 (n)428 (n) MacFadden1%0.99 · 0.96–1.01casesn/an/a Ma (PSW)74%0.26 · 0.07–0.89death3/36140/995 Ma (PSM)25%0.75 · 0.36–1.56ventilation12/36016/360 Yeh44%0.56 · 0.45–0.71progressionn/an/a Yeh37%0.63 · 0.53–0.75hosp.n/an/a Hunt67%0.33 · 0.25–0.43death73/3,9561,539/22,552 Cousins (PSM)50%0.50 · 0.29–0.85ventilation2,463 (n)2,463 (n) Cousins (PSM)51%0.49 · 0.35–0.68ICU2,463 (n)2,463 (n) Shestakova22%0.78 · 0.67–0.91deathpopulation-based cohort Loucera30%0.70 · 0.61–0.80death1,896 (n)14,072 (n) Chan59%0.41 · 0.12–1.44death400 (n)2,736 (n) Chan54%0.46 · 0.18–1.14severe case400 (n)2,736 (n) Chan42%0.58 · 0.17–1.91progression51/400798/2,736 Chan37%0.63 · 0.23–1.71progression400 (n)2,736 (n) Chan41%0.59 · 0.31–1.13progression196 (n)86 (n) Chan34%0.66 · 0.39–1.09progression196 (n)86 (n) Zaccardi34%0.66 · 0.60–0.72deathpopulation-based cohort Zaccardi31%0.69 · 0.65–0.73hosp.population-based cohort Yip (PSM)7%0.93 · 0.72–1.22death/hosp.8,604 (n)3,727 (n) Yip (PSM)15%0.85 · 0.68–1.07progression8,604 (n)3,727 (n) Yip (PSM)15%0.85 · 0.68–1.05progression8,604 (n)3,727 (n) Ouchi10%0.90 · 0.77–1.05death6,168 (n)9,875 (n) Ouchi8%0.92 · 0.82–1.02death/hosp.6,168 (n)9,875 (n) Morrison (PSM)41%0.59 · 0.41–0.84death2,684 (n)2,684 (n) Morrison (PSM)−16%1.16 · 0.76–1.76ventilation2,684 (n)2,684 (n) Morrison (PSM)3%0.97 · 0.72–1.31ICU2,684 (n)2,684 (n) Morrison (PSM)−4%1.04 · 0.84–1.28hosp.2,684 (n)2,684 (n) Mannucci38%0.62 · 0.41–0.93deathn/an/a Mannucci15%0.85 · 0.64–1.12hosp.n/an/a Milosavljevic33%0.67 · 0.47–0.95severe case377 (n)356 (n) Miao (PSM)1%0.99 · 0.85–1.15death233/796236/796 Miao (PSM)5%0.95 · 0.88–1.03hosp. time796 (n)796 (n) Servais49%0.51 · 0.34–0.78deathn/an/a Pinchera15%0.85 · 0.71–0.96severe case5/1914/24OT1 Sandhu3%0.97 · 0.95–0.99hosp.population-based cohort Yen (PSM)25%0.75 · 0.63–0.89death232/20,894295/20,894 Yen (PSM)25%0.75 · 0.60–0.95ventilation133/20,894168/20,894 Yen (PSM)19%0.81 · 0.70–0.94ICU332/20,894390/20,894 Yen (PSM)15%0.85 · 0.81–0.89hosp.2,820/20,8943,139/20,894 Yen (PSM)−2%1.02 · 0.94–1.10cases1,467/20,8941,364/20,894 Araldi60%0.40 · 0.32–0.50death107/2,598263/2,598 Akinosoglou37%0.63 · 0.35–1.13death147 (n)207 (n) Akinosoglou−39%1.39 · 0.79–2.45ICU147 (n)207 (n) Akinosoglou−3%1.03 · 0.62–1.69ARDS147 (n)207 (n) Alieva15%0.85 · 0.49–1.48hosp.375 (n)388 (n) Obiri-Yeboah−1%1.01 · 0.54–1.87death148 (n)381 (n) Obiri-Yeboah−4%1.04 · 0.67–1.59ventilation148 (n)381 (n) Obiri-Yeboah8%0.92 · 0.60–1.43ICU148 (n)381 (n) Piarulli53%0.47 · 0.20–1.08death/ICU1,444 (n)1,009 (n) Piarulli15%0.85 · 0.39–1.83death/ICU209 (n)180 (n) Piarulli45%0.55 · 0.40–0.75hosp.1,444 (n)1,009 (n) Greco22%0.78 · 0.57–1.05hosp.OT1 Greco26%0.74 · 0.60–0.92hosp.OT1 Greco17%0.83 · 0.46–1.50hosp.OT1 Guo62%0.38 · 0.15–0.92death/int.241 (n)330 (n) Guo81%0.19 · 0.06–0.56progression241 (n)330 (n) Guo80%0.20 · 0.04–1.03progression241 (n)330 (n) Zihono49%0.51 · 0.28–0.93death11/5631/81 Farah−3%1.03 · 0.83–1.28cases267/82169/218 Bidari10%0.90 · 0.65–1.23severe case29/80132/326 Miguel37%0.63 · 0.29–1.36ICU64 (n)68 (n) Miguel43%0.57 · 0.19–1.71ICU3/1514/40 Miguel31%0.69 · 0.23–2.04ICU6/495/28 Mamari50%0.50 · 0.29–0.86death11/3422/34OT1 Al-kuraishy78%0.22 · 0.06–0.77death3/609/40 Al-kuraishy41%0.59 · 0.45–0.78no recov.57 (n)31 (n) Al-kuraishy84%0.16 · 0.06–0.40no recov.57 (n)31 (n) Jang60%0.40 · 0.18–0.85death461 (n)95 (n) Jang72%0.28 · 0.11–0.72ventilation461 (n)95 (n) Jang39%0.61 · 0.33–1.13ICU461 (n)95 (n) Jang30%0.70 · 0.40–1.25oxygen461 (n)95 (n) Jang−27%1.27 · 0.70–2.29hosp.461 (n)95 (n) Lewandowski23%0.77 · 0.53–1.08death14/10183/329 Silverii29%0.71 · 0.27–1.90death220 (n)304 (n) Silverii20%0.80 · 0.49–1.28death220 (n)304 (n) Dimnjaković23%0.77 · 0.64–0.92hosp.2,843 (n)4,475 (n) Dimnjaković12%0.88 · 0.77–0.99cases2,843 (n)4,475 (n) Xu (PSM)52%0.48 · 0.23–0.83death405 (n)405 (n) Xu59%0.41 · 0.24–0.70death466 (n)4,456 (n) Xu54%0.46 · 0.26–0.81ventilation466 (n)4,456 (n) Xu72%0.28 · 0.08–0.96ARDS466 (n)4,456 (n) Olawore19%0.81 · 0.55–1.20PASC5,596 (n)1,451 (n) Olawore14%0.86 · 0.56–1.32PASC5,596 (n)1,451 (n) Chen81%0.19 · 0.05–0.80ICU2/12125/292 Chen39%0.61 · 0.42–0.89progression25/12199/292 Chen17%0.83 · 0.75–0.93hosp. time121 (n)292 (n) Hussein64%0.36 · 0.12–0.87death30/15860/110OT1 Johnson11%0.89 · 0.77–1.03progression Johnson21%0.79 · 0.71–0.88progression Johnson15%0.85 · 0.78–0.92progression Johnson13%0.87 · 0.66–1.14progression Johnson−4%1.04 · 0.97–1.11progression Harmon (PSW)18%0.82 · 0.75–0.90death4,667 (n)5,745 (n) Sakamaki23%0.77 · 0.72–0.82severe casepopulation-based cohort Somasundaram89%0.11 · 0.04–0.29death221 (n)200 (n) Chertok Shacham70%0.30 · 0.11–0.78death342 (n)515 (n) Matviichuk−5%1.05 · 0.85–1.26PASC155/31671/152 Benfathallah54%0.46 · 0.19–0.97death8/4130/74 Soff18%0.82 · 0.73–0.93PASC3,047 (n)4,383 (n) Johnson53%0.47 · 0.25–0.89PASC248 (n)248 (n) Liu64%0.36 · 0.20–0.64progression14/19891/444 Liu9%0.91 · 0.63–1.28hosp.38/198112/444 Liu15%0.85 · 0.62–1.13no recov.49/198147/444 Liu−1%1.01 · 0.90–1.09misc.152/198352/444 Felemban44%0.56 · 0.23–1.34ventilation10/827/32 Felemban9%0.91 · 0.38–2.16ICU14/826/32 Felemban35%0.65 · 0.26–1.64ARDS10/826/32 Felemban46%0.54 · 0.33–0.88no disch.82 (n)32 (n) Felemban64%0.36 · 0.26–0.50no disch.82 (n)32 (n) Ngiam20%0.80 · 0.68–0.96PASC Ngiam23%0.77 · 0.63–0.93PASC Butzin-Dozier39%0.61 · 0.51–0.73death Butzin-Dozier13%0.87 · 0.81–0.94PASC Butzin-Dozier10%0.90 · 0.68–1.20PASC Rodríguez-Fernán..31%0.69 · 0.49–0.96hosp.2,496 (n)2,630 (n) Rodríguez-Fernán..7%0.93 · 0.77–1.12cases3,035 (n)3,312 (n)
00.511.52+
1 OT: comparison with other treatment
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← Metformin
reduces risk
Metformin
increases risk →
Fig. S1. All outcomes.
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Fig. S2. Comparison of results for RCTs versus observational studies. For COVID-19 treatments, there is no significant difference between the results of RCTs and observational studies. Observational studies do not systematically over or underestimate efficacy. For high-cost treatments, there is a non-significant trend towards RCTs showing greater efficacy.