Two lots of hyaluronic acid can both be “>90% purity” and still behave completely differently in your formula. The reason is molecular weight. It decides how thick a solution gets, how the product feels on skin, and how the grade is used. This guide explains how to read molecular weight on a specification and how to choose a grade.
What molecular weight means for hyaluronic acid
Hyaluronic acid is a chain of repeating sugar units. Molecular weight tells you, on average, how long the chains in a lot are. It is given in daltons: kDa (thousands) or MDa (millions). Because every lot contains a spread of chain lengths, a specification normally gives a range or an average, not a single exact value.
Fermentation conditions influence the molecular weight a producer obtains, and controlling it is one of the challenges producers work on. [1] Lower molecular weight grades can also be made by breaking down longer chains; these are sold as hydrolysed HA.
The main grade families
| Grade | In solution | Typical role |
|---|---|---|
| High molecular weight (HMW) | Viscous, gel-like at low use levels | Surface film and texture in serums and creams; also used in oral supplement trials |
| Low molecular weight (LMW) | Thinner, less tacky | Leave-on hydration products, often blended with HMW |
| Hydrolysed / oligo HA | Very low viscosity | Toners, mists and other thin liquids |
There is no single industry cut-off between “high” and “low”. One supplier’s LMW can overlap another’s medium grade. Always compare the actual numbers.
Does molecular weight change the effect?
For topical use, the evidence says yes. A 2025 review reports that HA below about 100 kDa penetrates skin, and that lower molecular weights can reach the dermis. [2] High molecular weight HA mainly stays on the surface, where it forms a hydrating film.
A controlled trial supports the difference in practice. In 36 elderly people with dry skin, a lotion with low molecular weight HA raised skin hydration more than a high molecular weight HA lotion after four weeks. Water loss and symptom scores did not differ between the lotions. [3] It was a small trial in one group of people, so treat it as a guide rather than a rule.
For oral use, trials have used defined grades. A 2025 trial in 150 adults used sodium hyaluronate of 1.8 MDa at 60 or 120 mg a day for 12 weeks. [4] When you build an oral product on published research, match the grade used in the study as closely as you can. See oral hyaluronic acid supplements.
How molecular weight is reported on a COA
- Molecular weight range in kDa or MDa, usually from size-exclusion chromatography.
- Intrinsic viscosity (for example in m³/kg), measured by viscometry. It rises with chain length, so it is often used in place of, or alongside, molecular weight.
- The method. Different methods give different numbers for the same lot. Two values are only comparable if the method is the same.
Choosing a grade: a buyer’s checklist
- Define the job: texture and surface film, thin-liquid hydration, or an oral active.
- If you follow a study, note the molecular weight and dose it used.
- Ask for the molecular weight range or intrinsic viscosity, with the method.
- Check the assay basis (as sodium hyaluronate, hyaluronic acid or glucuronic acid) and the method.
- Check protein content, loss on drying, pH of a solution, heavy metals and microbiology.
- Run a stability check in your base. Very long chains can lose viscosity over time under heat, acid or some actives.
Not sure whether you need hyaluronic acid or sodium hyaluronate? Read the comparison.
What the research says
- A 2025 review of microbial HA production notes that fermentation now dominates supply and that molecular weight is one of the key factors producers work to control. [1]
- A 2025 review of topical HA reports that HA below about 100 kDa penetrates skin, with lower molecular weights able to reach the dermis. [2]
- In a 4-week double-blind trial in 36 elderly people with dry skin, low molecular weight HA lotion raised skin hydration more than high molecular weight HA lotion or the plain lotion. [3]
- A 12-week trial in 150 healthy adults used oral sodium hyaluronate of 1.8 MDa; 120 mg a day improved skin hydration and elasticity versus placebo. The trial was run by a sodium hyaluronate producer. [4]
These summaries describe published research on the ingredient. They are not claims for any finished product; claims on finished products must meet the rules of the market where they are sold.
References
- Marwan-Abdelbaset E, et al. Microbial production of hyaluronic acid: the current advances, engineering strategies and trends. J Biotechnol. 2025;403:52-72. doi:10.1016/j.jbiotec.2025.03.015
- Zanchetta C, et al. Hyaluronic acid in topical applications: the various forms and biological effects of a hero molecule in the cosmetics industry. Biomolecules. 2025;15(12):1656. doi:10.3390/biom15121656
- Muhammad P, et al. Effectiveness of topical hyaluronic acid of different molecular weights in xerosis cutis treatment in elderly: a double-blind, randomized controlled trial. Arch Dermatol Res. 2024;316(6):329. doi:10.1007/s00403-024-03003-2
- Dolečková I, et al. Oral sodium hyaluronate improves skin hydration, barrier function and signs of aging: a randomized, double-blind, placebo-controlled trial in 150 healthy adults. Sci Rep. 2025;16(1):2941. doi:10.1038/s41598-025-32758-5
Need a specific molecular weight?
Tell FC Materials the molecular weight range, application and volume you need. Our team will confirm availability and send the specification and COA.
