RDH stands for Registered Dental Hygienist.
The letters go after a hygienist's name once a state board has issued them a license to practice dental hygiene — they're a license title, not a degree.
Every state licenses dental hygienists, and the letters the law protects differ by state: Michigan's rules spell out when a hygienist may use 'R.D.H.', and Indiana recognizes 'L.D.H.', 'R.D.H.' and 'D.H.'.
This page covers what the credential takes and how to read it on job posts.
RDH = Registered Dental Hygienist
RDH stands for Registered Dental Hygienist.
When the letters appear after someone's name, they signal that a state licensing board has issued that person a license to practice dental hygiene — and in the states that define the letters in law, using them is tied directly to holding that license.
Michigan defines the letters in its administrative rules: a registered dental hygienist who holds a degree or certificate from a CODA-approved dental hygiene program and has completed all licensure requirements may use the letters "R.D.H." after their name (Michigan Administrative Code R 338.11233).
California's statute works from the other direction — it says only a registered dental hygienist (an RDH, an RDHAP or an RDHEF) or a licensed dentist may practice dental hygiene or perform hygiene procedures on patients, such as scaling, with narrow listed exceptions (California Business and Professions Code section 1915).
What the job behind the letters involves — the cleanings, scaling, sealants, x-rays and patient education — is covered in our dental hygienist career guide.
This page stays on the credential itself: what RDH means, what it takes to use the letters, and how they relate to the other abbreviations you'll see in a dental office.
License title, not a degree
Because the letters sit next to degree abbreviations on name badges and business cards, RDH gets mistaken for an academic credential.
It isn't.
The degree is the education you complete; the RDH is the license a state issues once you've cleared its requirements.
BLS describes the sequence plainly: every state requires dental hygienists to be licensed, and in most states that means a dental hygiene degree from an accredited program plus passing written and clinical examinations — the degree qualifies you for licensure, but the license is what lets you practice.
Michigan's rule shows the two joining in a single sentence: the "R.D.H." letters follow both the degree or certificate from the CODA-approved program and the completion of all licensure requirements.
You can finish a hygiene program and still not be an RDH — the letters arrive with the license, not the diploma.
It isn't a national credential either.
The license comes from one state's board, which is why the letters, the title rules and the requirements all shift at state lines.
And in most states the license isn't permanent on issuance — continuing education is part of keeping it (BLS).
Title rules are state law
How you earn the RDH
In most states, three things stand between a hygiene student and the letters, and BLS sums them up: a dental hygiene degree from an accredited program, passing written and clinical examinations, and continuing education to keep the license once it's issued.
The education step: BLS lists the associate degree as dental hygiene's entry-level education, and says dental hygiene associate degree programs usually take 3 years to complete.
The written exam is the NBDHE, the National Board Dental Hygiene Examination, which is intended to fulfill or partially fulfill the written examination requirement for dental hygiene licensure in all states.
On the clinical side, ADEX — the dental hygiene licensing exam from the American Board of Dental Examiners, formerly CDCA — consists of a manikin-based clinical exam plus a computer-based simulated clinical exam, and is open to students or graduates of CODA-accredited programs.
Which programs and exams satisfy your state is a board question: the state-by-state detail lives in our hygienist requirements by state pages, and the full start-to-finish walk-through is in how to become a dental hygienist.
Once the board issues the license, continuing education — the third piece above — is what keeps the letters current.
RDH vs LDH and other state titles
RDH isn't the only set of letters state law uses for hygienists, though — and the differences are easy to get wrong.
Indiana is the example worth knowing.
Its hygiene statute (IC 25-13-1-11) treats anyone who uses the titles "Licensed Dental Hygienist" or "Dental Hygienist," or the letters L.D.H., R.D.H. or D.H. in connection with their name, as practicing dental hygiene.
That means Indiana law recognizes LDH as well as RDH — the statute lists several protected abbreviations for the same license rather than substituting one for another.
Michigan puts its letters in administrative rules (Michigan Administrative Code R 338.11233), as covered above.
Maine goes a step further and names titled roles built on the hygiene license: state law defines an "independent practice dental hygienist" and a "dental therapist" (plus a "provisional dental therapist"), each a person who holds a Maine dental hygienist license with additional authorization (Maine Revised Statutes, Title 32, section 18302).
California splits its hygiene licenses into named categories — RDH, RDHAP and RDHEF — in California Business and Professions Code section 1915.
The through-line: whatever the letters, each one traces back to that state's license to practice dental hygiene.
What varies from state to state is the label the law uses and the extra authorizations it layers on top.
Other letters you'll see (BSDH, RDHAP, MSDH)
The alphabet soup after a hygienist's name is part licensure and part education, and knowing which is which tells you whether you're looking at someone's legal authority to practice or their schooling.
- BSDH — Bachelor of Science in Dental Hygiene. A degree, not a license. It matters most where a bachelor's opens doors: BLS says a bachelor's or master's degree is usually required for research, teaching, or clinical practice in public or school health programs.
- MSDH — Master of Science in Dental Hygiene. The graduate version of the same degree. BLS notes master's programs in dental hygiene are relatively uncommon.
- RDHAP — Registered Dental Hygienist in Alternative Practice. Not a degree — a separate California license category. Qualifying is a step beyond the RDH: under Bus. & Prof. Code 1922(a), the applicant passes a California law and ethics exam and, on the main route, holds a current California RDH license, has practiced dental hygiene for at least 2,000 hours during the preceding 36 months, and holds a bachelor's degree or equivalent plus at least 150 hours of additional board-prescribed education. Each element is required on that route — the statute does not let an applicant swap the hours for the degree.
- RDHEF — Registered Dental Hygienist in Extended Functions. The third California hygiene category named in the same statute (Bus. & Prof. Code 1915).
For the full side-by-side — what RDHAP adds, what it takes to qualify, and how the two licenses differ in practice — see RDH vs RDHAP.
What 'RDH required' means on a job post
Hygiene postings compress all of this into three letters: "RDH required," "RDH license in good standing," "must hold a current RDH."
Decoded, it's the practice saying it needs someone who holds that state's hygiene license — the legal authority to practice — rather than someone with a particular degree.
The license isn't a nice-to-have for this work; it's the entry ticket.
Every state requires dental hygienists to be licensed, and some states put the point beyond argument: California's statute allows only a registered dental hygienist (RDH, RDHAP or RDHEF) or a licensed dentist to practice dental hygiene or perform hygiene procedures such as scaling, with narrow listed exceptions.
A hygiene job in California is, by construction, a job for one of those licensees.
Expect the letters to be checked, too.
Licenses are verifiable — California's DCA License Search, for example, covers dental credentials well beyond the dentist license, including the Registered Dental Hygienist and the RDH in Alternative Practice / Extended Function categories.
The license isn't the only requirement you'll see in posts, either: BLS notes many hygienist jobs also require CPR certification.
Degree letters in a post ("BSDH preferred") describe an education preference; the license letters describe whether you can legally do the work at all.
If you hold the license the post names, you meet its core requirement — you can see the pattern across current dental hygienist jobs.
This article is general career information, not legal advice. Title and licensing rules are state law — confirm specifics with your state dental board.