low lithium levels

hi just wondering if anyone can enlighten me please.. I came off quetiapine to go onto lithium started on 400mg the past 2weeks my bloods have shown iv got low lithium levels.. I don't understand what this means if iv only been on it for 4weeks ??.. and don't see my consultant for another 2 weeks .. thankyou for reading.

thankyou Im not that much clued up on this at all... I thought 400mg was quite a high dose with being on 400mg of quetiapine before.. iv been given a sooner date now to see the consultant.

hi
thankyou ...
the consultant doubled the dose to 800mg see how I go with that..maybe reduced after 2weeks of blood tests.

thankyou I will .