Calcium hydroxylapatite (CaHA) is a mineral naturally found in human bone that, in a purified synthetic form, is used as an injectable dermal filler. Best known by the brand Radiesse, it works in two ways: the gel it is suspended in adds volume straight away, while tiny CaHA microspheres prompt the skin to build its own collagen over the following months. This dual action—immediate lift plus gradual, natural collagen stimulation—makes it a distinctive option among cosmetic injectables.

At a glance

What it is: An injectable filler made of calcium hydroxylapatite microspheres in a gel carrier
Brand name: Radiesse (manufactured by Merz Aesthetics)
How it works: Immediate volume from the gel, then biostimulation of the skin’s own collagen
Common areas: Jawline, chin, cheeks, nasolabial folds and hands; hyperdiluted for the neck and décolleté
How long it lasts: Generally around 12–18 months, sometimes longer
Good to know: Fully biodegradable but not reversible the way hyaluronic acid fillers are

What is calcium hydroxylapatite?

Calcium hydroxylapatite is a naturally occurring mineral—the same calcium-and-phosphate compound that makes up much of our bones and teeth. As an injectable, it is produced synthetically as smooth microspheres (roughly 25–45 microns across) suspended in a water-based carboxymethylcellulose gel; in the widely used formulation the microspheres make up about 30% and the gel carrier about 70%.^[1][2] This is a different class of filler from hyaluronic acid. Rather than only holding water to create volume, CaHA also acts as a scaffold that works with the body’s own tissue—which is why it is described as a biostimulatory, or “regenerative,” filler.

How CaHA works: two actions in one

CaHA has a dual mechanism. First, the gel carrier provides immediate volume and lift at the moment of treatment. Then, over the following weeks, the gel is gradually absorbed while the CaHA microspheres remain and stimulate the skin’s fibroblasts to produce fresh collagen (both type I and type III), along with elastin and other supportive proteins—a process known as neocollagenesis.^[1] New collagen formation has been observed beginning around four weeks after injection and continuing for many months.^[2] So the early result comes from the gel, and the longer-term result comes from the patient’s own regenerated tissue.

What CaHA is used for

Because it is a firmer, more structural filler, CaHA is well suited to restoring volume and definition in areas that benefit from support. Common uses include softening deeper folds such as the nasolabial lines, restoring midface and cheek volume, and defining the jawline and chin.^[1][2] It is also widely used for hand rejuvenation, replacing lost volume on the back of the hands. In a more diluted (“hyperdiluted”) form, CaHA is spread over larger areas to improve overall skin quality and firmness on the neck and décolleté rather than to add distinct volume.^[1] The choice of technique depends on the goal, which is why an assessment matters.

How long it lasts — and is it permanent?

CaHA is long-lasting but not permanent. Aesthetic results generally last in the region of 12 to 18 months, and sometimes longer, as the stimulated collagen gradually turns over.^[2] The material itself is fully biodegradable: the gel carrier is absorbed within weeks, and the microspheres are eventually broken down into calcium and phosphate ions and cleared by the body’s own cells.^[2] One important distinction from hyaluronic acid fillers is that CaHA cannot be quickly dissolved with an enzyme—there is no equivalent of hyaluronidase for it—so careful, conservative placement by an expert injector is especially important.

CaHA and other biostimulators

CaHA sits within a group of collagen-stimulating (biostimulatory) injectables. It is often compared with poly-L-lactic acid, another biostimulator that prompts gradual collagen production. The key practical difference is that CaHA also delivers immediate volume through its gel carrier, whereas poly-L-lactic acid works almost entirely gradually with little instant result. Both differ from standard HA fillers, which primarily add volume by attracting water. Understanding which category a product belongs to helps set realistic expectations about how quickly—and by what mechanism—a result appears.

Safety, and CaHA in Canada

CaHA has an established safety record, with most side effects being mild and temporary—bruising, swelling, redness or tenderness at the injection site.^[2] As with any dermal filler, the most serious (though uncommon) risk is injection into or compression of a blood vessel, which is why deep anatomical knowledge and proper technique are essential. In Canada, injectable fillers are regulated as licensed medical devices; Radiesse is authorized by Health Canada, and in June 2025 Merz Aesthetics received Health Canada approval to use it for moderate wrinkles of the décolleté area.^[3] Treatment should only be performed by a qualified, trained injector using authorized products. At Revel, injectables are offered through our face treatments. This entry is educational and does not replace an individual clinical assessment.

Related glossary terms

Clinical & editorial sources

Nowag B, Casabona G, Kippenberger S, et al. The Role of Calcium Hydroxylapatite (Radiesse) as a Regenerative Aesthetic Treatment: A Narrative Review. Aesthetic Surgery Journal. 2023;43(10):1063–1090. doi:10.1093/asj/sjad173
Jacovella PF, et al. Calcium Hydroxylapatite: Over a Decade of Clinical Experience. The Journal of Clinical and Aesthetic Dermatology. jcadonline.com
Merz Aesthetics Canada. Merz Aesthetics Receives Approval from Health Canada for RADIESSE as an Aesthetic Injectable for the Treatment of Moderate Wrinkles in the Décolleté Area. 3 June 2025. businesswire.com

This glossary entry provides general educational information and does not replace an individual clinical assessment or medical advice.

Clinically reviewed by: Leah Zawawi, RPN | Medical Aesthetics & Injectables.

Last reviewed: August 2026.