My pdoc had my blood drawn when I started taking 300mg of lithium at night as an adjunct, and I know my level was 0.3.
I just looked up the therapeutic range, and read it's 0.7-1.2 ng/dl.
I'm willing to bet that your pdoc isn't ordering a lithium level be drawn now because there's a very low possibility of toxicity at the dose you're taking.

I'm sorry you're feeling so shitty