Are there other human trials testing metformin during acute COVID?

The short version: the evidence you retrieved does not answer whether other human trials besides ACTIV-6 have tested metformin during acute COVID for long COVID prevention.

The 2025 scoping review [1] mentions a single "2023 preventive study suggesting reduced PASC incidence when used around acute infection" but does not name the trial, give its sample size, or list any other human trials testing metformin during acute COVID. The review calls the evidence "insufficient" and says "trials focused on PASC patients" are still needed [1]. That is the only mention of metformin for this purpose in your records.

The other two records are irrelevant to your question. One is a case report of metformin-associated lactic acidosis in a binge-drinking man [2]. The other is a case report of liver disease where metformin was used as part of a metabolic intervention, not during acute COVID [3]. Neither tests metformin for long COVID prevention.

The retrieval surfaced no other human trials testing metformin started during acute SARS-CoV-2 infection for long COVID outcomes. That does not mean none exist — it means these searches did not find them. The scoping review [1] implies at least one other study exists (the unnamed 2023 trial), but gives no details to evaluate it.

My call: the evidence here does not identify any other human trials beyond what the scoping review vaguely references. Confidence: low — the retrieval is thin and the one relevant mention is too vague to assess.