Choosing a hyaluronic-acid (HA) filler is not a one-number exercise. Rheology helps describe how a gel behaves, but no single measurement can identify the best product for every person or treatment area.
Image note: The accompanying visual is an AI-generated illustration, not a photograph of a real patient, clinician or treatment.
Four terms worth understanding
- G′ (elastic or storage modulus): Describes the gel's elastic response and how it tends to recover after deformation. It is useful context, not a universal score for lift or suitability.
- G″ (viscous or loss modulus): Describes energy dissipated as the material deforms. It complements G′; the two are not interchangeable.
- Viscosity: Describes resistance to flow under specified test conditions. It is not another word for cohesivity.
- Cohesivity: Describes how strongly the gel holds together. Tests and reporting methods can differ between manufacturers.
Cross-linking, HA concentration, particle structure and manufacturing technology also influence a product's measured behaviour. Results from different laboratory methods may not be directly comparable.
Put the numbers in clinical context
A 2022 review of filler rheology notes that G′ may relate to lift among products with similar composition or technology, but the relationship is not consistent across products with different formulations. Rheology should inform—not replace—clinical judgment.
For qualified practitioners, a considered comparison starts with the treatment objective and patient assessment, then checks the exact product's instructions for use, authorized indications, supporting evidence, handling requirements and traceability. Anatomy, tissue characteristics, patient history, local rules and the clinician's training all matter. There is no reliable universal chart that maps one G′ value to one facial area.
Safety is part of product selection
Dermal filler injection is a medical procedure. Temporary effects such as swelling and bruising are common; serious complications, including unintended injection into a blood vessel, are uncommon but can cause lasting injury. Products are authorized for specific uses, which vary by country. Patients should seek a suitably licensed, trained health-care professional and discuss the product's labelling, alternatives and risks before treatment.
A practical comparison checklist
- Is the product authentic, traceable and authorized for the intended use in this jurisdiction?
- Are the test methods and data comparable, or are the figures being presented without context?
- Does the product's evidence and labelling fit the clinical objective and patient assessment?
- Are storage, consent, documentation, follow-up and complication arrangements in place?
Further reading
- Fundarò et al., review of HA filler rheology and physicochemical characteristics (2022)
- U.S. FDA: dermal filler uses, labelling and risks
Browse the SwiftGlamour product catalogue. Always check current product documentation and local authorization before professional use.
