It doesn't say physical or magical, just damage.

Its magic.

Teemo's abilities all deal magic damage, but if he is buying attack damage items, then his auto attack will do a lot more physical than magic damage.

FYI, if you're going by the death recap, his auto attack shows under 'Toxic Shot' and is actually a mixed damage, if he's building AP then most of the damage is likely magic, if AD physical. It's one of the few abilities that you can't actually tell by just looking at it the damage type.

This is what is happening, luckily you can look at his items, if he has all AP items you can bet he's doing mostly magic damage, if he has all phisical damage items well get armor. It should show the damage seperately but than the game might count it as a casted spell, although it would give hilarious results with reylas it would probably be OP.

PS: in most champions normal builds you should have an item or 2 for defense, for example getting an atma's impailer for phisical damage or zhonyas ring for magic damage for getting magic resist, get a hexdrinker for phisical damage or abyssal scepter, upgrade for a purely defensive item if need be, if they have a fed phisical damager, you might need thornmail.

even if you play a teemo who is building ad, his attacks will poison you from his magic damange, so you should consider building regular and magic armor if you're playing teemo, but i suggest not to do that unless your a tank or something. If your character usually doesnt build much armor and stuff just gank teemo early on

Blinding Dart- magic
Auto Attack- Physical
Poison on Auto Attack- Magical
Shrooms- magical

Yes yes, but as I said, it's hard to differentiate between the physical and magical damage of his toxic shot, as they're both combined in the death recap.