This medical valve (1) comprises a body (2) provided with at least two female connectors (5a, 5b) and a male connector (6), a mobile plug (3) which is mounted in the body (2), is provided with a rotation lever and comprises a fluid circulation channel, and a reinforcement collar (7) which is rigidly connected to at least two of the connectors (5a, 5b, 5c, 6). The reinforcement collar (7) is spaced apart from the body (2) in order to form an openworked zone around the central body (2). The invention also relates to a kit for preparing a product to be injected, preferably a mixture or an emulsion, said kit comprising such a medical valve (1). The invention also relates to a method for preparing a mixture or an emulsion with the aid of such a medical valve (1).