It depends on what your expectations are. If you are accustomed to earning the salary of a medical engineer with 3 years experience and expect to get near that

It depends on what your expectations are. If you are accustomed to earning the salary of a medical engineer with 3 years experience and expect to get near that as an entry programmer with no experience (which is essentially what everything you listed boils down to from a recruiters perspective), then its going to be a very difficult road and you will have to work much cheaper than you want to. Certifications only help for specific fields like cisco network engineers or certain types of admin jobs, in my experience little if at all for programming positions. So i wouldnt go that route. I would suggest any of the other things you listed to get experience (internship, freelance, work cheaper). You will have to work your way up, but thats pretty much always the case whenever you jump ship into a new field. Id also suggest trying your luck at a startup since they usually dont have strict HR processes like larger companies, and might be willing to overlook lack of exp if you can bring good engineering skills, and other qualities (passion, etc.) to the table. If you gave more info on where you are or want to work (EU country, US, south america, etc) and what programming field you want to work in (web, embedded, etc) we could give you better help.