“Hyperdilute Radiesse” is the same calcium hydroxylapatite filler that has been approved in the US since 2006, mixed with extra liquid before injection. The aim changes with the mix: instead of filling a fold, a thin layer of microspheres spread under the skin is meant to prompt the body to lay down collagen across a wider area. About 3,000 US searches a month ask about it (clickstream estimate, October 2026). This page sets out what the dilution tiers mean, the one use FDA has approved, the trial behind that approval, and what remains off-label, as of 14 October 2026. It is not a recommendation; whether any injectable suits a person is a decision for a qualified clinician.
What is being diluted
Radiesse is smooth calcium hydroxylapatite (CaHA) microspheres, roughly 25–45 micrometres across, suspended in a carboxymethylcellulose gel and supplied ready to inject. The gel is absorbed over weeks; the microspheres stay longer and are the part credited with the collagen response. Our Sculptra vs Radiesse page covers the material and its approval history; our biostimulators page places it among the other collagen stimulators.
Dilution has no single standard, but the field uses the vocabulary of a 2018 global consensus panel (Goldie et al., Dermatologic Surgery 2018):
| Preparation | Ratio of Radiesse to added liquid | Stated purpose |
|---|---|---|
| Undiluted (as supplied, sometimes with lidocaine mixed in) | 1:0 | fill folds, add volume, contour |
| Diluted | 1:1 | lift and support with some spread |
| Hyperdiluted | 1:2 or more | spread thinly for skin quality and laxity |
The added liquid is sterile saline, often with lidocaine for comfort. A Brazilian consensus the following year applied the same idea to the face and body (de Almeida et al., Plastic and Reconstructive Surgery Global Open 2019), and a narrative review published on 12 October 2026 organises the published protocols into a taxonomy of preparations and injection maps by area, noting “substantial heterogeneity” in preparation, technique and outcome measures across studies (Lin and Lin, Aesthetic Plastic Surgery 2026). That heterogeneity is the main limit on the evidence: two clinics saying “hyperdilute” may not mean the same mix.
The one approved use, dated
FDA regulates Radiesse as a device through premarket approval PMA P050052. Its approval record, read through FDA's database on 14 October 2026, shows the uses added over time:
| Date | Supplement | What FDA approved |
|---|---|---|
| 22 Dec 2006 | original | undiluted, for moderate to severe facial wrinkles and folds such as nasolabial folds |
| 13 Jul 2009 | S019 | instructions for mixing with 2% lidocaine before injection (a final concentration of 0.3% lidocaine) |
| 4 Jun 2015 | S049 | volume loss in the back of the hands |
| 1 Sep 2021 | S129 | Radiesse (+): loss of jawline contour, adults over 21 |
| 31 Mar 2026 | S162 | diluted 1:2 with 0.9% sterile saline, subdermal, for décolleté wrinkles, age 22 and over |
The 2026 supplement is the first time FDA has approved Radiesse as a diluted preparation for any area (openFDA PMA record). It is narrow: one ratio, one diluent, one area. A 1:2 mix on the neck, jawline, arms, abdomen or buttocks is still off-label, as is any other ratio on the chest. The 2018 consensus paper said as much of its own recommendations, calling body biostimulation with diluted CaHA a “novel off-label use”.
The trial behind the approval
The pivotal study is registered as NCT05163353 and published as Fabi et al., Aesthetic Surgery Journal 2026. Merz North America sponsored it; two of the six authors are Merz employees and one is a Merz biostatistician.
| Item | As registered and reported |
|---|---|
| Who | 152 women with moderate to severe décolleté wrinkles, enrolled from December 2021 |
| Design | randomized; 116 treated straight away (up to three sessions, optional retreatment), 36 left untreated until week 24, then treated |
| Blinding | outcome assessors only; participants knew whether they had been treated |
| Primary measure | a one-point or better improvement on the Merz Aesthetics Scale for décolleté wrinkles at rest, week 24 |
| Result | 71.2% responders treated vs 6.3% untreated (95% CIs 61.4–79.4% and 1.5–22.9%) |
| Wrinkles in motion (secondary) | 65.8% vs 16.0% |
| Follow-up | to week 84; study completed June 2025 |
The registry lists every adverse event reported in at least 5% of a group and every serious one. Among 116 treated women: abnormal visual-acuity test results in 9, injection-site bruising in 7, COVID-19 in 3; serious events in 2 women, recorded as a worsened existing condition, an animal bite and a hip deformity. Among the 36 untreated women there were no serious events. The registry does not say any serious event was caused by the treatment, and the published report describes reactions as predominantly transient, mild to moderate injection-site reactions.
What the design can and cannot say: a blinded assessor saw a clear difference between treated and untreated chests at six months. It does not compare diluted Radiesse with any other treatment, with undiluted Radiesse, or with a saline injection, so it cannot separate the product's effect from the effect of needle passes under the skin. And it tested one ratio in one area; it is not evidence for the other ratios and sites clinics use.
Why imaging was part of the trial
Calcium hydroxylapatite shows up on X-ray, and the décolleté sits above breast tissue screened by mammography. The trial included a retrospective review of post-treatment breast imaging and reported “no interference attributable to diluted Radiesse”. Merz has also registered a dedicated 30-woman study to examine breast imaging after treatment (NCT07086248); on 14 October 2026 it was listed as active and not recruiting, with no results posted. Anyone with breast imaging scheduled would reasonably tell the radiologist about any chest injection.
How much of the evidence there is
A PubMed search on 14 October 2026 joining hyperdilution to calcium hydroxylapatite or Radiesse returned 53 records; restricting any diluted form of the product to randomized controlled trials returned 4, and none of the diluted-CaHA records was retracted. Much of the rest is consensus statements, reviews, technique papers and small case series, many with industry-affiliated authors, covering stretch marks, forearm skin, the neck, the buttocks and the face after weight loss. Those papers describe what clinicians do; outside the chest, they are not controlled evidence that it works.
What “hyperdilute” does not mean
It does not mean a different product, a weaker safety profile or an easier procedure — the microspheres are the same, there is no dissolving agent for calcium hydroxylapatite, and the consensus papers place the injection under the skin with a cannula or needle in planes a clinician chooses. It does not mean the effect is immediate: the stated mechanism is a collagen response that builds over weeks, which is why the trial measured at 24 weeks. And on the label in the US it means one thing only — 1:2 with saline, for chest wrinkles. Questions about sagging, fillers and collagen stimulators more broadly are set out on our Sculptra vs filler page and collagen injections page.
Sources and dates
Opened 14 October 2026: FDA's PMA database record for P050052 (all 170 supplements read for indication changes); ClinicalTrials.gov records NCT05163353 (results) and NCT07086248; PubMed records 42424535 (Fabi 2026), 42864549 (Lin 2026), 30358631 (Goldie 2018) and 31044123 (de Almeida 2019), and the counts stated above. Corrections go to the contact page.