Question abt meds

Patient: I am a diabetic and am currently taking metformin and Lantus 10 mg at bedtime. I have been having some discomfort in my upper back. I got some over the counter Doans pills to take for it but it says if taking a prescribed diabetic medication consult a dr. before taking. I just want to know if it is safe for me to take the Doans? Thank you.

Doctor: