MD Codes Filler: What Do the Codes Mean?

An MD Code is a short label, such as Ck1, for one injection point on the face: in the 2021 paper that first described the system in a peer-reviewed journal, each code carries the target depth, the tool (needle or cannula), the injection technique and a minimum product amount. MD Codes is a planning and teaching method for hyaluronic acid (HA) filler, not a filler product, and which points apply to your face is decided at the exam.

There are other ways to look at MD Codes, such as how long filler lasts or what it costs, but this article explains one thing: what a single code marks and what it leaves out. Every number below comes from published papers, not from STON Clinic patients.

What Does an MD Code Stand For?

What Does an MD Code Stand For?

Each code names one injection site. The 2021 paper explains that the MD Codes are letters, numbers, shapes, and colors, and that the letters signify anatomical units (e.g., the cheek, temple, or chin) and the numbers signify subunits. Its own example: the cheek is represented by the letters Ck, and subunits of the cheek are numbered, so Ck1 = zygomatic arch and Ck2 = zygomatic eminence. The paper also marks the side of the face, so the same point on the right and left can be told apart.

Behind each label sits a set of instructions. According to the paper's summary, each MD Code includes information regarding the target depth of injection, the proper delivery tool (needle or cannula) and delivery technique (e.g., aliquot, bolus, fanning), and the minimum product volume recommended to achieve visible, reproducible results, which the author calls the active number. In short, a code is shorthand that lets two injectors mean the same spot, layer and method.

What Do the Layer and Tool in a Code Tell You?

What Do the Layer and Tool in a Code Tell You?

They tell you where the product is meant to sit and how it gets there. Some codes aim at the bone surface (supraperiosteal, meaning just on top of the bone), others at the layer under the skin. The FDA notes that approved dermal fillers are supplied for injection using a syringe with a needle or cannula, and the code says which of the two the method suggests for that point.

The table lists a few codes from the 2021 paper's own table, with the caution note the paper attaches. It describes the author's method, not a plan for any one person.

The paper lists other options for some of these sites, and other units (chin, jawline, forehead, nose) have their own codes. The point of the table is the pattern: one code ties one spot to one layer and one tool.

What Do the Layer and Tool in a Code Tell You?

Why Are Some Codes Red?

Why Are Some Codes Red?

Red marks an alert area. The paper says that MD Codes in red denote alert areas, where there are sensitive structures, such as neurovascular bundles in facial danger zones. These red codes remind the clinician to be cautious in these areas when using needles and to consider the use of cannulas instead, and the paper adds that the alert codes should never be used to guide injection by novice clinicians.

That caution lines up with what the FDA calls the most concerning risk of dermal fillers: unintentional injection into a blood vessel, leading to blocked blood vessels and poor blood supply to tissues. A red code is a reminder for the injector. It does not mean the area is off limits, and a code without red does not mean a point carries no risk.

Is MD Codes a Filler Product?

Is MD Codes a Filler Product?

No. It is a method for describing and planning HA filler injections. The 2021 paper describes itself as the first peer-reviewed description of the MD Codes system and its algorithms, and its author, Maurício de Maio, has served as a consultant for Allergan plc, a filler maker.

So "MD Codes filler" does not name a syringe or a brand. The product, the amount and the depth are separate choices. The FDA notes that the time that the effect lasts depends on the filler material and the area where it is injected, and the code itself does not change that.

How Strong Is the Evidence Behind MD Codes?

How Strong Is the Evidence Behind MD Codes?

It is early and comes mostly from the people who built the method. The 2021 paper rated its own level of evidence as IV and illustrated the system with three case studies. A later retrospective analysis looked back at 12 adult women from the Netherlands who were treated with about 12 mL of HA fillers each at an MD Codes training event, with patients selected based on their appropriateness for the training. All authors were consultants for the filler maker whose products were used.

These are small groups under their own conditions, and the 9-month answers are the patients' own questionnaire replies. They describe those participants, not what one person will see. The 2025 commentary argues that such methods may neglect the underlying skeletal asymmetries, and that a comprehensive approach that includes a detailed assessment by skilled practitioners is essential.

Does the Code Number Set the Order or the Amount?

Neither, on its own. The 2021 paper states that the MD Codes numbers do not reflect the sequence in which the injections should be administered, but instead provide a checklist of items that the clinician can mark when assessing each facial unit. Ck3 is not the third injection; it is the third box on the cheek checklist.

Order comes from the algorithms layered on top. The paper says codes are selected using algorithms focused on lessening a saggy, tired, sad, or angry look, and a narrative review of the eye area describes how the method identified which points should be prioritized to cause greater aesthetic impact. The "active number" in each code is the author's suggested minimum, not a dose set for your face.

Does the Code Number Set the Order or the Amount?

Questions Worth Asking About a Code-Based Plan

If a clinic mentions codes or points, the useful questions are about your face, not the label. Ask which areas the plan covers and why, which layer each point targets, whether a needle or a cannula is planned near alert areas, and how swelling or a blocked vessel would be checked and handled. The FDA also suggests you ask your health care provider about their training and experience injecting dermal fillers.

STON Clinic's Hyaluronic Acid Filler Page

STON Clinic's page on hyaluronic acid filler says that how long it holds depends on the product, the area and your own condition, and that whether a treatment suits you is decided by the physicians after an examination, with results and side effects varying from person to person.

Filler consultations are available at Lotte Hotel Seoul Main Tower 9F, 30 Eulji-ro, Jung-gu, Seoul, in Myeongdong near Euljiro 1(il)-ga Station on Line 2.