One of the most challenging aspects of being a psychiatrist is treating patients who do not want to be treated. People will ask me what are the options they can do if their loved ones are sick, but not wanting to take medications. This situation is not uncommon.
In some psychiatric conditions (schizophrenia in particular comes to mind) patients often do not think they are sick or have anything wrong with them. Thus, they will not take medications. Trained clinicians and law enforcement can place people on 5150 holds and take them to the hospital if their illnesses get so severe that they are at risk to hurt themselves, hurt other people, or too sick to care for themselves. So, friends or family members, even people of the community, can call 911 if they see someone that impaired.
There is an option for a long-acting injectable as well. A medication that can be taken once a month or once every three months for those that are not wanting to take a pill everyday. This is usually used in cases of schizophrenia, schizoaffective or bipolar disorder. In some states, like in NY, there can even be court-mandated treatments for the mentally ill to take these medications.
In more mild to moderate cases, it's important for family and friends to encourage the sick to take medications as prescribed and go to their doctor's appointments.