It would help if you could fill in your profile so which know which Type of Diabetes you have and what medications you are taking (if any) for it - this information will mean people can give a more directed reply
Undiagnosed Type1 often causes weight loss, undiagnosed Coeliac Disease caused me to slowly but surely lose weight, but there are probably many things that could cause it, so we need a few more details from you
Edit: so after writing that I realised you've posted in the T1 section, doh, how have your blood sugar levels been, high levels and not enough insulin may be contributing