I'm glad you're asking if it's ok to take this. As the other posters have said, you should check with a health professional first whether combing it with metformin or just taking it alone.
Read the health risks for this supplement here:
/en.wikipedia.org/wiki/Spirulina_(dietary_supplement) I think it would be best to take the metformin as prescribed and alter your diet to lower carb and engage in regular sustained exercise as well as resistance training along with weights.
Your health is important, so please be careful about
supplements.