Hi BlindBetta. Given the symptoms you are describing, you really need to talk to your psychiatrist immediately. Since it is the weekend, if you continue to feel quite unwell, then you really should consider Moose's advice.

The first time I was put on Lithium, I was also put on 1,200 mg, straight away (no titration). It's hard for me to remember/discern how I initially reacted because I was also going through alcohol withdrawal and mixed manic. I was eventually taken off because of hypothyroidism and mood issues, but a couple years later put back on again, but 900 mg, like you. That time I do remember having nausea problems for a while, though not to the point of vomiting. I'm not sure if it was toxicity or what, but it did ease. I remember easing the nausea with OTC meds. Have you considered talking to your pharmacist about your situation and asking if there is anything that can help? Are you drinking plenty of liquids?