N-of-1 trials therapeutic tests allow an objective evaluation of treatment efficacy in a single patient. Thereby, they can support off-label prescriptions, or promote treatment safety and efficiency in chronic patients through the deprescription of useless drugs. They also encourage active participation of patients in their medical care. Practically a treatment is compared to a placebo in double blind during a series of randomly alternating periods. Statistical analysis comparing measurements performed in the patient throughout the test enable to evaluate objectively treatment efficacy. The performance of this type of test is now offered to patients and practitioners by the Service of Clinical Pharmacology in the University Hospital of Lausanne.