Hair loss from weight loss or illness, how to treat it?

If you get a patient who is experiencing hair loss after an event like an illness or a diet change/weight loss or medication-related, how do you reverse hair loss in such cases? Is the hair loss medication the same?

First you tackle the cause like stabilizing weight loss with a good diet or treat whatever the illness was that precipitated the hair loss. Most of the time the hair loss will reverse unless, for example, weight loss induces genetic hair loss that was hidden from you.  Then we use the standard medication for hair loss such as finasteride and/or minoxidil (topical or orally).