When do you drink a potion?

When in fast combat bosses, when do you drink potions?

Just wondering because it's hard to calculate levels while checking on health/other shit. If I was botting I'd just get the level and the real level, if the level is less than real level +5 then drink, but doing maths while eating/shit is hard.

Though, now I think about it it can't be too hard because I wrote this while doing frost dragons.

Since I'm jewish, I wait until I'm 99 again then I repot.

i do at half of what it gives bonus's too.