during episodes of low blood sugar, or if you're allergic to insulin. allergic reaction may occur and may be life threatening. don't reuse needles or share insulin pens, even if the needle has been changed. the most common side effect is low blood sugar, which can be serious and life threatening. it may cause shaking, sweating, fast heartbeat, and blurred vision. check your blood sugar levels daily while using toujeo®. injection site reactions may occur. don't change your dose or type of insulin without talking to your doctor. tell your doctor if you take other medicines and about all your medical conditions. insulins, including toujeo®, in combination with tzds (thiazolidinediones) may cause serious side effects like heart failure that can lead to death, even if you've never had heart failure before. don't dilute or mix toujeo® with other insulins or solutions as it may not work as intended and you may lose blood sugar control, which could be serious. toujeo® helps me stay on track with my blood sugar. ask your doctor about toujeo®.