It's actually a rather complex question, IMO. Perhaps first and foremost it may well depend on what your intentions are regarding seeking a formal diagnosis. If you're seeking or considering government entitlements, most assuredly you'd need a professional diagnosis to validate financial support. Then again if you're just curious and want to know for your own edification, a formal diagnosis may not be the best of options if your resources in securing one is limited.
Though I think anyone should be aware of the potential consequences of seeking and securing such a diagnosis as well. The possibility that once you are formally diagnosed through a professional medical system, that your neurological profile becomes
a matter of record, for better or worse. Whether a formal diagnosis ends up being of assistance to you, or
officially stigmatized with a "scarlet letter", can't be guaranteed one way or another IMO.
And of course what may heavily influence both available government entitlements as well as the potential consequences of being formally labeled autistic, is whatever nation you reside in relative to its social welfare system in place. If it involves a national healthcare system it may not take up significant resources for you to obtain such a diagnosis, although you may predictably have to wait a long time to secure it.
Then again if you're living in the United States, we have no national healthcare system comparable to nations like the UK or Canada. Where you may have to simply shell out thousands of dollars for a proper diagnosis from a psychiatrist or neurologist. In essence, someone who at the least holds an M.D.. Depending of course on whatever healthcare plan you may or may not have.
And perhaps above all to be wary of the DSM-V diagnostic protocols, where you just might discover that it functions more as a system to restrict or deny a positive diagnosis rather than to confirm it. To realize how limited support for autistic adults can be depending where you are in the US. In my state as is the case with many others, you may find that autism programs are something geared to help children- not adults. Where it may appear as if there's no such thing as an autistic adult.