From the Guidelines
There is no direct equivalent of 8 insulin units to metformin dosage as these medications work through completely different mechanisms. Metformin cannot be substituted for insulin on a unit-for-unit basis. Metformin works by decreasing hepatic glucose production, reducing intestinal glucose absorption, and improving insulin sensitivity, while insulin directly lowers blood glucose by facilitating cellular glucose uptake.
Key Considerations
- For patients with type 2 diabetes considering a transition from insulin to metformin, a typical starting dose would be 500 mg once or twice daily, gradually increased based on blood glucose response and tolerability, potentially up to 2000-2500 mg daily divided into 2-3 doses 1.
- This transition should only occur under medical supervision with frequent blood glucose monitoring, and is generally only appropriate for type 2 diabetes patients with some remaining pancreatic function.
- Patients with type 1 diabetes cannot substitute metformin for insulin as they require insulin for survival.
Dosage and Administration
- The maximum effective dose of metformin can be up to 1,000 mg twice per day but is often 850 mg twice per day 1.
- A longer-acting formulation of metformin is available in some countries and can be given once per day 1.
- Preprandial levels that are in range, post-prandial levels, usually measured 90–120 min after a meal, may be checked to achieve A1C levels in the target range 1.
From the Research
Metformin Equivalent to Insulin Units
There is no direct equivalent of metformin to insulin units, as metformin and insulin work through different mechanisms to lower blood glucose levels.
- Metformin improves insulin sensitivity, reduces hepatic glucose production, and increases glucose uptake by muscles 2, 3, 4.
- Insulin, on the other hand, directly lowers blood glucose levels by facilitating glucose uptake by cells.
Comparison of Metformin and Insulin
While there is no direct conversion from insulin units to metformin, some studies suggest that metformin can be used in combination with insulin to improve glycemic control and possibly reduce insulin requirements 2, 4.
- A study published in 1997 found that metformin-sulfonylurea combination therapy was as effective as insulin or insulin plus sulfonylurea in improving glycemic control 2.
- However, the exact equivalent of 8 insulin units in terms of metformin dosage is not established in the available literature.
Available Dosage Information
The available studies provide information on the typical dosages of metformin used in clinical trials, but not a direct conversion to insulin units.
- A study published in 2017 used an average dose of metformin immediate release (IR) of 2,000±1,000 mg/day and metformin extended release (XR) of 1,000±500 mg/day 5.
- However, this information does not provide a direct equivalent to 8 insulin units.