Can I just call my insurance company and ask if they'll cover a specific medication?

Here's the short version of my question without having to read a novel:
I have Blue Cross Blue Shield of Tennessee. Doc said it was fine to take two vyvanse doses during the day, but she says my insurance won't cover the second dose. I know for a fact that she didn't confirm that with my insurance company. Can I just call my insurance company and directly ask if they will cover the second dose, or is that something only my doctor/their staff can do?

Here the little back story that goes with it:

I take 70 MG of Vyvanse in the morning and 20 mg of Adderal in the afternoon, but as of late, they've both become basically ineffective in helping my Inattentive ADHD (no hyperactivity). The Adderal is definitely not great, as it gives me some weird side effects that the Vyvanse doesn't (kind of makes me feel a little frantic, but not anxious, headaches, difficulty swallowing), but I need to take something at around noon every day, even though the Adderal is usually completely unnoticeable within an hour and a half of taking it. I've tried to take an extra Adderal in the afternoon, but it didn't do much to help and just gave me more side effects.
I've been interested in trading my afternoon Adderal for another Vyvanse. My doctor is okay with this, but has assured me that my insurance will not cover two doses of Vyvanse per day. But when I checked the drug coverage list for my insurance online, it lists Vyvanse as one without a quantity limit. I've mentioned this twice to my doc, but each time she casually mentioned that it wouldn't be covered and never actually check with my insurance. So my question is: Can I call my insurance company directly and ask if a second dose will be covered under my plan, or is that something that only my doctor/their staff can do? If I can call and ask and it turns out it can be covered, how do I get a confirmation of that so I can be completely positive when I tell my doctor?

I have needed to have a few meds pre authorized this way in the past, I always got what was needed. Just paperwork, and annoying.

Sure you can call your insurer... just get the name (they'll probably only give you a 1st name.) Write down the date, the time you spoke with the representative, & the name they give you, as well as what they told you. Realistically though, there may be no way to be absolutely 100% positive the insurance company will pay. Someone higher up the food chain, at the insurance company, could look at the claim & decide it's not valid for some reason. Most insurance companies say that they will not guarantee payment until they receive, & come to a decision with regard to, the bill. At least this has been my experience.

Call member service (BCBSTN) at 1-877-673-9165 for drug question, they also can provide the number on how to file a protest

Ask the insurance what steps you need to take to get this medication covered for these dosages and ask about filing a prior authorization; AND ask how/where you doc needs to contact them to get the prior authorization to get the second dose approved. Get this information to your doc to file. It has to come from the doc. They will typically cover it then. Good luck!

Since all of these medications are controlled substances my insurance will only cover a certain dosage. Like with mine which BCBS of Texas, it will cover Ritalin for 20 mg a day but only if I get it prescibed in the 10mg tablets which I take one in the morning a half at noon and another half at 3. It won''t cover the 5mg tabets which I would take two in the morning, one at noon and one at 3. There both the same thing but for some reason the insurance doesn't see it that way. It would be so much better if I could just get it filled at the 5mg dose but then that would be too easy, I guess.

So it would certainly be good to ask them what dosages they cover as well.