Do not use Lantus to treat diabetic ketoacidosis.Important Safety Information for Lantus (insulin glargine [rDNA origin] injection) Do not take Lantus if you are allergic to insulin or any of the inactive ingredients in Lantus. You must test your blood sugar levels while using insulin, such as Lantus. Do not make any changes to your dose or type of insulin without talking to your healthcare provider. Any change of insulin should be made cautiously and only under medical supervision. Do NOT dilute or mix Lantus with any other insulin or solution. It will not work as intended and you may lose blood sugar control, which could be serious. Lantus must only be used if the solution is clear and colorless with no particles visible. Do not share needles, insulin pens or syringes with others. The most common side effect of insulin, including Lantus, is low blood sugar (hypoglycemia), which may be serious. Some people may experience symptoms such as shaking, sweating, fast heartbeat, and blurred vision. Severe hypoglycemia may be serious and life threatening. It may cause harm to your heart or brain. Other possible side effects may include injection site reactions, including changes in fat tissue at the injection site, and allergic reactions, including itching and rash. In rare cases, some allergic reactions may be life threatening. Tell your doctor about other medicines and supplements you are taking because they can change the way insulin works. Before starting Lantus, tell your doctor about all your medical conditions including if you have liver or kidney problems, are pregnant or planning to become pregnant, or are breast-feeding or planning to breast-feed. Lantus SoloSTAR is a disposable prefilled insulin pen. Please talk to your healthcare provider about proper injection technique and follow instructions in the Instruction Leaflet that accompanies the pen.