Question about sentence construction

Hi all,
I would need an help to understand the construction of this sentence:

薬を飲んだらどうですか

That should mean: “why did you take the medicine?” (I don’t know if it’s correct, actually)
The main issue for me is to understand the verb construction:

飲んだらどうですか

and above all the use of だらどう, because I don’t understand if it’s the join of だら and どう, or if だ is part of 飲んだ (past of 飲む) and then what is らどう.

So, I’m a little lost and actually I need help ^_.

Thanks!