or if you're allergic to insulin. get medical help right away if you have a serious allergic reaction such as body rash, or trouble breathing. don't reuse needles, or share insulin pens. the most common side effect is low blood sugar, which can be life-threatening. it may cause shaking, sweating, fast heartbeat, and blurred vision. check your blood sugar levels daily. injection site reactions may occur. don't change your dose without talking to your doctor. tell your doctor about all medicines and medical conditions. check insulin label each time you inject. taking tzds with insulins may cause heart failure that can lead to death. ♪ let's groove tonight. ask your doctor about toujeo.