Which of the following is not a task a non-veterinarian can perform?

Diagnosing medical conditions is a task that is strictly reserved for licensed veterinarians. This responsibility requires extensive clinical training, knowledge of veterinary medicine, and the ability to interpret diagnostic tests and clinical signs accurately. Veterinarians are uniquely qualified to evaluate an animal's health status, determine the nature of any medical conditions, and develop treatment plans.

In contrast, the other options can be performed by non-veterinarians under appropriate circumstances. Administering medications, for example, can often be carried out by veterinary technicians and trained staff as long as they are following a veterinarian’s instructions. Providing nutritional advice can also be done by trained staff, especially in contexts such as pet retail or certain veterinary settings, as long as it adheres to veterinary guidance. Additionally, performing basic health checks, such as weighing animals and taking vital signs, can also be done by non-veterinarian staff, as it does not involve making a medical diagnosis. Thus, the act of diagnosing medical conditions stands apart as a task exclusively for veterinarians.