The VEN classification classifies inventory items in categories based on their importance for the patients or clients. These categories are: Vital - Essential - Non-essential. Vital items are potentially life-saving or crucial products with a major public health importance. They also contain medicines with a significant withdrawal side-effect. Essential items are those which are effective against less severe but significant forms of disease. Non-essential items are those used for minor or self-limited illnesses. They are the least important items to be stocked. Sometimes a country or an organisation has insufficient funds to buy all the desired medicines. The VEN analysis is a well-known method to help set up priorities for purchasing medicines and keeping stock.