Lithium oral and dehydration is it normal?

Hi, so after a two month manic episode followed by a two month depressive episode i was started on 400mg of lithium. I’m now on 1200mg of lithium. I have been on lithium since the starting dose of 400mg for around three months now. I have been on 1200mg of lithium for around two months now.

At first i was slightly dehydrated all the time.

Now im only dehydrated 1-3 hours after taking lithium (i take it at night). It feels like moderate-severe dehydration. I just want to drink everything in sight and cant stomach food while im that dehydrated.

I take my lithium around 8:30pm.

Is this dehydration normal? Will it go away?

I have no other notable side effects and dont want to stop lithium becauase its the best thing ive been on, ever.

i get my blood checked and its in the therapeutic range

just to add i probably drink at least 3 litres of fluids per day - ive recently drastically reduced my caffeine intake - and the salt i sometimes use is lo-salt