Pulmonary clearance not approved yet for surgery

So I am working on my 6 month diet program before i can get the approval from my insurance for gastric sleeve. I still have 2 more months to go. I have not been approved yet, but am working with a surgeon. I scheduled a pulmonary clearance on october 6th. My question is, should i be doing all the these things to get ready for surgery, even if i haven't been approved yet. & how far in advance is too advance for this pulmonary clearance?

I am in a 6 month program, I recently found out the cardiologist clearance is good for 90 days,  surgery date set for mid December so i am walking a fine line.

It would be best to check with Dr and insurance company.

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