If you think you might have an eating disorder and you tell your GP about this, here are some of the things that they may do for you.
They will check for physical causes first
After listening to you describe your symptoms, the GP probably won't give you a diagnosis. Instead, they might run a few tests to find out if there is some other medical condition that you might have, whose symptoms might be similar to those associated with the eating disorder you think you're suffering from. They might also closely examine any medications you've recently started taking, to find out if they might be causing the issue.
For example, if you have suddenly developed an insatiable appetite, and you're now binge-eating every day, then your GP might conclude that this is caused by the new contraceptive pill you've started taking (as the hormonal changes this medication induces can sometimes make women feel much hungrier) or by a thyroid condition you've recently developed.
Conversely, if you've lost your appetite and your weight is plummeting, your GP won't assume this is because you have anorexia but will instead run tests to check for things such as cancer or a stomach ulcer, either of which could cause this issue.
They will provide advice and some referrals
If after running several tests, closely examining your medical history and the list of medications you're on, your GP can find no other cause for your symptoms, then they might give you an eating disorder diagnosis or they might book you an appointment with an eating disorder specialist who may be better equipped to diagnose you. If they think it's necessary, they might refer you to both a counsellor and a dietitian as well.
They may offer some basic nutritional and psychological advice, too; for example, if they suspect your restriction of your food intake becomes more severe when you're stressed, they might advise you to practise using safer stress-reduction methods, like taking hot baths, going jogging or confiding in a loved one.
Finally, they may also make a plan to run certain medical tests regularly whilst you're recovering. These tests will allow the GP to check that your eating disorder isn't causing damage to your body (such as diabetes if you're binge-eating, nutritional deficiencies if you're restricting or electrolyte imbalances if you're bulimic) and to ensure that if you do develop medical issues because of this disorder, that they detect them very quickly.
For more information, reach out to a GP.