I highly recommend not using lithium without medical supervision. All of the bipolar people I know have significant side-effects from it. You also need to be careful with hydration because lithium toxicity is dangerous. If you get confusion as a side-effect of toxicity, you become less able to recognize what is happening.

From my own experiences with atypical anti-psychotics, getting dehydrated or running low on carbohydrates can affect my motor control severely enough that I can't drive. (I always have water and energy bars on me.) It resolves within an hour after rehydrating.

Interactions with other medication or supplements can also be dangerous.