Also, confirm with your doctor that taking metformin irregularly is fine with the formulation you are using. Mine is long-acting, and so is not meant to control sugars per dose but as a maintenance medication to keep my blood sugars in line.
One thing to remember is that one study is hardly evidence that there is any issue, and a doctor will also have access to your bloodwork to determine if you have any other pre-existing medical conditions that would prevent you from using creatine.
As another anecdote (which is all the reference 'study' from above is) - I take metformin, and use creatine regularly. My blood work has always been normal, and my doctor knows I take creatine and has no issue with that.
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