I am planning pregnancy. Should I take some vitamins?

Consider taking Folic Acid (it is usually taken in 3-6 month before pregnancy and during first trimester of existing pregnancy).

I have a sister that craves sugar, she will even wake at night and if there isnt anything sweet to eat she will spoon sugar into her mouth from the sugar bag. her bloods have ruled out diabetes. She is forever on a diet, could lose 6 pounds one week but put up 8 the following week, vwey worried about her, could she be lacking in something?

This is a very serious situation. You should talk to your sister and make the following steps: 1) Talk to psychologist. Maybe she will advice something to overcome 'sugar hunger'. 2) Start treatment with appetite suppressants like Phentrimine. It is available without prescription and will help to stop these carvings and lose weight instead of gaining it. Weight gain is very harmful in case of your sister because extra fat increases insulin resistance of cells. Good luck and health to your sister!

Your sister may need serious psychotherapeutic treatment to overcome excessive appetite for sweets. Do not leave her alone in this situation and maybe the doctor will prescribe her some medication which will help to control appetite.