Toujeo SoloStar and Toujeo Max SoloStar are a pair of brand names for insulin glargine. This medication is a long-acting insulin that's used for diabetes in adults and children. It's a more concentrated version of insulin glargine containing 300 units/mL. It comes as prefilled pens that you use for once-daily injections under the skin. Side effects include common cold symptoms and low blood sugar.