support teemo?

The short answer is generally going to be the same as the answer to this question: "Are you a Diamond Player in Gold climbing up on a smurf?"

The longer answer is that Teemo doesn't actually have anything worthy of note as an actual support. Annie gets away with it because of her stun, but Teemo's blind, despite being against marksmen doesn't last long enough to matter nearly as much as other support options, and unless your whole team is communicating with you via VOIP programs, your mushrooms aren't going to be as useful in a team fight as a Janna, or Sona ult. Additionally you're squishy, and until level six you don't have anything of actual value as a support.

Plus because of your poison you have to worry about accidentally taking your marksman's kills, and potentially their buffs. Additionally your mushrooms slow is nice, but its not a team fight winner on its own, it NEEDS the damage to matter. The vision range on them isn't enough to have them act as wards either.

Teemo is good/annoying top because he gets to build items that turn his shrooms into monsters, and top champions generally don't have a good way of dealing with him. This also means that if Teemo gets a kill with his mushrooms its very beneficial to the team. Since Teemo is top he can also roam out of his lane a bit, and use his mushrooms to protect his tower, allowing him to venture out and do his job with his mushrooms elsewhere as well. In a duo lane Teemo doesn't really have this ability because his Marksman should be getting the farm, not him, and leaving the Marksman alone is just asking the enemy to tower dive them.

So essentially unless you're vastly better than the league you're in, it isn't worth it.

I've tried this a couple times in normals, here are my thoughts.

His harass is hilarious.

The blind is of limited usefulness.

His shrooms make useful wards if you know common gank paths, but you should still put actual wards down.

Without a ton of snowballing he won't have enough gold to do anything late game. Even top lane teemo runs into problems of not being able to do that much in teamfights.

HOWEVER: If you get your teams permission to do this and combo it with somebody with lots of early game damage it turns into a terrifying kill lane.