飲んでるの

are you drinking?

→ 飲む
phrase Common #3,391
are you drinking? A casual contraction of 飲んでいるの. The subject is often omitted; with medicine, 飲む means “take” rather than “drink.” の gives the question a conversational, explanatory tone.
JA: 何を飲んでるの?
EN: What are you drinking?

牛乳を飲んでるの?

Are you drinking milk?

お酒飲んでるの?

Are you drinking?

なんでお酒を飲んでるの

Why are you drinking?

— 紅夢 (1991)

どうして、こんな薬を飲んでるの?

Why are you taking this kind of medicine?

何を飲んでるの

What are you drinking?

— エリート・スクワッド (2007)

飲んでるのか?

Are you drinking?

— きっと、うまくいく (2009)

薬飲んでるの?

Are you taking any medication?

ワインを飲んでるの?

Are you drinking wine?

トムはコーヒーを飲んでるの?

Is Tom drinking coffee?

緑茶を飲んでるの?

Are you drinking green tea?

何飲んでるの?

What are you drinking?

もう何年もこの薬を飲んでるの。

I've been taking this medication for years now.