Soylent and Theranos are two recent counterexamples that come to mind. In the former case, a company made many claims they have since dialed back; and in the latter case, outright fraud, though it may not have started out that way.

23andMe were shut down for a period by the FDA.

There are of course plenty of healthcare startups that are working within the established boundaries of the existing system, but if you want to push those boundaries, it's going to take a while for regulations to catch up, and in the meantime caveat emptor.