Drug Test for a new job

Okay, I want to start off that I have ADHD and anxiety so maybe I’m just extra nervous and overthinking but I could use some advice.

So I had an in person interview earlier this week on Monday. It went super well and the manager implied he wanted me on the team, I said great, I can start as soon as possible. I got the call next day Tuesday that I’ve been given an offer and I said yes, and got the onboarding process started. I was told that it requires a drug test and I didn’t think it would be a problem since I have a prescription for vyvanse 70mg. I even let my psychiatrist know and was given their office contact info in case anyone needed to speak with them.

Now here’s the problem: the background check company that issues the drug screen has this listed on their FAQ: “A laboratory positive drug test must be reviewed by a Medical Review Officer (MRO); therefore, the MRO process takes between 3 to 5 business days. This process could be extended depending on the result, RX/medical documentation provided and the complexity of the documentation's verification process.”

I have the drug test scheduled for today, May 8. They want me to start my new job May 18. If the process could take up to 5 business days or longer, could this raise any red flags at the company I’m about to start at? Should I contact someone at the screening company to expedite this process? Should I ask to extend the start date?

I just want this whole onboarding process to go smoothly and my biggest fear is that the offer will be rescinded… any advice is appreciated!!!!