You need more extensive evaluation than just a series of blood tests. Such excessive weight loss without trying indicates a serious underlying problem. This could be cancer, chronic infection, liver or kidney disease, thyroid disease, parasites, or a variety of other conditions. Sometimes a search for these conditions needs to be done, such as screening chest x-ray, endoscopy, or other studies depending on findings on physical exam. You might want to see a specialist for further evaluation such as an internal medicine doctor. Hope this helps.