My fiance has schizophrenia and rarely wants sex. is this normal behaviour?

Schizophrenia: Being schizophrenic is not a normal existence. But if your fiance is taking his medications and working in treatment, his illness can get & stay in remission. If not, his illness may interfere with his ability to relate to you, including sexually. Also, sometimes the medications can interfere with libido as well. You can encourage him to keep working with his doctors and therapists.

Maybe: I don't know if it's normal, but it is common. Often times and unfortunately, the antipsychotic medications for schizophrenia have, as side-effects-decreased libido or problems with impotency or both. It is a real problem as often, the person will stop their medication because: "it messes with my nature." one can have their testosterone level checked. Supplements can then be given if indicated.

Schizophrenia: Not uncommon in schizophrenics, either result of illness or effect of medications used to treat the illness.