Hi Pauline, Thanks for using Healthcaremagic, You have been detected to overactive thyroid that is thyrotoxicosis which means I presume your T3 and T4 levels are high and rightly advised antithyroid drug. This drug is generally well tolerated and your Physician is starting with low dose in case you have any undesirable effects please report them to your treating physician. Allergic rashes and pruritus are common, these can often be treated with antihistamines without stopping the carbimazole. Bone marrow suppression should be monitored with blood counts and if not tolerated then alternative Propylthiouracil can be used. In over active thyroid state weight is lost due to high metabolism but that is not desirable so if you gain some weight take care by diet and regular walking. Once Thyroid levels are controlled surgery if possible is one of the option and also radioactive iodine therapy discuss with treating Doctor. Hope this helps. Take care Good Luck Dr.Akhilesh Dubey M.D.