There are many prescription versions of supplements but they’re often rarely prescribed because of cost unless there is a specific need. Prescription meds are actually regulated though (supplements are not regulated in any way) so they are superior, albeit far more costly. But because supplements are unregulated there is no way to be sure the advertised dosage is correct, or the advertised compound is even present (though some manufacturers do independent testing tbf)

Take vitamin d for example. Most Americans (and most people in the world, tbh) are deficient. But your doctor will likely tell you to just get vitamin d supplements even though prescription cholecalciferol exists. That is typically only used for serious deficiencies, like if you need 50,000iu weekly. But it is manufactured in more traditional dosages like 1-2000iu for daily use.

But in America for a great deal of people who are either uninsured, underinsured, or even with decent insurance cholecalciferol will almost always be significantly more expensive than simply buying a supplement vitamin d3, so the supplement is recommended. And this is one of the cheapest possible examples. Deplin vs levomefolic acid for example is much more dramatic of a price difference