Do Not Take Metformin While Actively Vomiting with Flu A
You should NOT take your metformin right now while you are actively vomiting—hold the medication until you can tolerate food and fluids, and focus on staying hydrated. 1
Why You Should Hold Metformin During Active Vomiting
The American Diabetes Association explicitly recommends temporarily discontinuing metformin if patients experience persistent nausea, vomiting, or dehydration. 1 This is a critical safety measure, not just a comfort issue.
Metformin's gastrointestinal side effects (nausea, vomiting, diarrhea) are already common and can worsen when you're unable to take it with food. 1, 2 Taking it on an empty stomach during active illness will likely make your nausea significantly worse and perpetuate the vomiting cycle.
While metformin-associated lactic acidosis is extremely rare (0.03 per 1,000 patient-years), the risk increases when you're dehydrated or acutely ill. 3, 4 Vomiting creates dehydration and potential acute kidney stress, which impairs metformin clearance.
Managing Your Blood Sugar of 223 mg/dL
Your blood sugar of 223 mg/dL, while elevated, does not require emergency insulin initiation. Current guidelines recommend considering insulin when blood glucose is ≥300 mg/dL or A1C >10%, especially with symptoms of severe hyperglycemia (excessive urination, thirst) or weight loss. 3
Your elevated glucose is expected during acute illness like influenza—stress hormones and illness naturally raise blood sugar even without your usual medications. 3
Focus on hydration first: Small, frequent sips of fluids containing electrolytes and some carbohydrates (like diluted juice, sports drinks, or broth) will help prevent dehydration and avoid further blood sugar spikes from dehydration-induced stress. 1
When to Restart Metformin
Resume metformin only when you can tolerate solid food and are no longer vomiting. 1 Start with a small meal, then take your usual dose with that meal.
If you've been off metformin for 24-48 hours, you can restart at your usual dose once eating normally—no need to retitrate. 1
Extended-release formulations cause less GI upset than immediate-release if you continue to have nausea issues. 5
Red Flags Requiring Emergency Care
You should go to the emergency department if you develop:
- Blood glucose persistently >300 mg/dL despite hydration 3
- Inability to keep down any fluids for >12 hours (severe dehydration risk) 1
- Rapid breathing, confusion, or severe abdominal pain (potential diabetic ketoacidosis, though rare in type 2 diabetes) 3
- Signs of severe dehydration: decreased urination, extreme weakness, dizziness when standing 1
Key Reassurance
Metformin does not cause hypoglycemia—it's an "antihyperglycemic" agent, not a hypoglycemic one. 6, 4 Missing doses for 1-2 days during acute illness will not cause dangerous low blood sugars.
Your blood sugar will likely normalize once the flu resolves and you resume normal eating and medication. 3
Holding metformin temporarily during acute vomiting illness is standard medical practice and will not lead to long-term complications. 1