Metformin (brand name: Glucophage) will be in your system for 96.8 hours which is approximately 4 days.

Metformin has an elimination half-life of approximately 17.6 hours.
It takes approximately 5.5 x elimination half-life for a medicine to be cleared from your body which is
5.5 x 17.6 hours = 96.8 hours for metformin.

However other factors to consider include:
1. How much and how often you have taken the drug.
2. Your metabolic rate – a slower metabolism will increase the time a drug remains in your system.
3. Your age and health – older age and poor health will generally increase the time the drug stays in your system.
4. Body mass – generally the bigger you are the longer a drug will remain in your system.

For more information see:
https://www.drugs.com/pro/metformin.html