There are so many different possible side effects. You should contact the Lithium Information center in Madison, Wisconsin. They are online. You can also find information in medical online searches.
My ex took a very large dose of lithium and his side effects were short-term memory loss, trembling of his hands, and being very thirsty. But he was a big guy and took a very large dose.
Girlfriend
Lithium doses is more based on blood level rather than dose. So if I am right about this, a higher dose would be closer to a blood level of 1.4. A lower dose would be around 0.6. So when you ask about side effects make sure you ask about level.
My level is 0.7 and only experience significant weight gain (unusualy high, 40lbs but looks more like 10-20) dry-mouth and occasional loose poop especially after an increase.
Lithium has had a very positive anti-depressant quality, however it was left below level for a while and I started to swing some, I think. So I may need to have a higher dose or an additional mood stabilizer for a while.
When I started taking lithium I was in a mixed episode, and cleared symptoms very quickly, I started seeing improvemnts after the second day.
Lithium, along with Risperdal and Zoloft have returned my life back in order. Even now that I am cycling at a good rapid pace with some mixing I am still not showing enough symptoms to be even called "hypomanic".