A formulary is the list of prescription medications that an insurance plan covers. Each insurer and each provincial drug program maintains its own formulary, and they can differ significantly. Drugs on the formulary are organized into tiers that determine how much the insurer will reimburse. Tier 1 typically includes generic drugs with the highest reimbursement, while higher tiers include brand-name or specialty medications with lower reimbursement or prior authorization requirements. If a medication is not on your plan's formulary, you will likely pay the full cost out of pocket unless you obtain special authorization from the insurer. Formularies are updated regularly as new drugs are approved by Health Canada and as generic alternatives become available.