A shot of Dupixent can cost as much as $3,354—or more, in some cases. Your insurance company may deny your prescription for Dupixent because it is not on the formulary list, or because they don’t believe the drug is medically necessary for your condition. Your physician can prepare a medical exception letter to send to the insurance company, telling it the drug is medically necessary for your condition. If the insurer still denies Dupixent, an appeal could be your next course of action.