There are 1000 of Health related Blogging websites that accept free Guest Post, however your health article should be unique to get it approved by the website owner.
No body likes Plagiarism content, even Google hates plagiarism.
Above are top health related blog websites to post your content and increase Backlinks.
If you are having Health related Websites or Blog, you should consider having backlinks in high authority Health Blogging Websites to improve SEO ranking of your website.
Guest Blog Outreach Campaign is very useful for SEO Digital Marketing.