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Since your husband do not have any liver / kidney or heart failure lactic acidosis from a single dose of metformin is highly unlikely. When used according to current prescribing recommendations, the risk of metformin -induced lactic acidosis is close to zero. But these symptoms appears to be metformin related side effect. You need not be overly worried about this, but a judicious observation is recommended.

Watch from any drowsiness, further drop in BP below 110/70 mmHg, breathlessness, palpitation, severe sweating, lethargy and severe vomiting. If there is any of these symptoms or if the currents symptoms are NOT showing sings of resolution in 8-12 hours you SHOULD get medical help (ER/Urgent care).

As I said earlier this could be a drug reaction other than lactic acidosis. You need to inform this to your Doctor. Metformin is an excellent and safe drug. In many individuals these symptoms will disappear with a lower dosage and a modified regimen. So it is better not to write off metformin based on this reaction alone If not Metformin another Oral anti diabetic has to be considered. This is best done by your Doctor. Do let me know if you need assistance in this.

Hope this helps
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