A serum usually relies on a blend of hyaluronic acid molecular weights rather than a single grade. High-molecular-weight HA rests on the skin surface for immediate hydration and a smoother feel, while low and oligo HA reach the upper skin layers and support moisture there. Using one grade alone is possible, but most brands prefer a blend because it covers both the surface and the upper skin at once. The right mix depends on your target product, the claims you want to support, and the skin feel you are aiming for.
What hyaluronic acid does in a skincare formula
Hyaluronic acid (HA) is a naturally occurring substance in the skin that declines with age. In cosmetics it is used as a humectant — an ingredient that attracts and holds water in the upper skin layers. That supports surface hydration and a plumper, smoother appearance. It is a standard cosmetic ingredient in major markets and is not a drug, so any claims around it should stay cosmetic rather than therapeutic.
Why molecular weight changes the result
Molecular weight (MW) describes the size of the HA molecule. Because the outer skin layer limits what passes through easily, size is the main reason different HA grades feel and behave differently. The table below shows the common groupings.
| Grade | Common MW range | Where it acts | What it is used for |
|---|---|---|---|
| High (macro) HA | about 1,000–1,800 kDa | Surface / film | Immediate surface hydration, smoother feel |
| Low / mini HA | about 10–300 kDa | Upper skin | Light feel, supports upper-layer moisture |
| Oligo HA | below 10 kDa | Upper skin | Skin feel and compatibility in blends |
High molecular weight HA: surface hydration
High-MW HA is too large to move through the stratum corneum easily, so it stays on top. There it forms a light, breathable film that helps the skin hold water and gives an immediate smoothing and plumping feel. That is why many serums list it near the top when the goal is surface hydration and a dewy finish.
Low and oligo HA: upper-skin moisture
Smaller HA grades are more able to reach the upper epidermis. They are often chosen for a lighter skin feel and for supporting moisture in the upper layers. Claims about deeper action should stay conservative — the evidence that supports cosmetic use is strongest at the surface and upper skin, not below.
Sodium hyaluronate versus hyaluronic acid
You will often see sodium hyaluronate on an ingredient list. It is the sodium salt of HA and is typically more stable in a formula, so many manufacturers use it interchangeably. Functionally it is a similar humectant; the choice between the two is usually about formulation stability and labeling rather than a different skin benefit.
Typical use levels and how brands blend grades
Use levels vary by formula, but leave-on cosmetics commonly use HA at roughly 0.1% to 2%, often as a blend of two or more molecular weights. A blend lets a product combine the surface film of high-MW HA with the lighter feel of low-MW HA.
- High-MW HA for immediate surface hydration and a smooth finish
- Low-MW HA for a lighter feel and upper-layer moisture support
- Oligo HA to round out the blend’s skin feel
- Glycerin or other humectants to reinforce water attraction
- An emollient or occlusive to slow water loss from the skin
Formulation and claim tips for private label
- HA is water-soluble, so it is added in the water phase of the formula.
- Very high-MW HA can be sensitive to heavy shear; gentle mixing protects the viscosity.
- Pair HA with emollients or occlusives so the attracted water stays in the skin.
- Keep claims cosmetic: "hydrates", "supports moisture", "smooths the look of fine lines" — not therapeutic wording.
- Most modern cosmetic HA is fermentation-derived, which fits vegan and clean-positioned claims.
How to choose the right HA for your product
Start from the product goal. A gel or serum that promises a dewy surface finish leans on high-MW HA. A lightweight lotion that targets daily moisture support can lean on low-MW HA, often in a blend. If you are building a private label line, match the molecular weight mix to the target market’s claim rules and to the skin feel your customers expect, then confirm the level with stability testing. Document the chosen grades and use level in the specification so the manufacturer can reproduce the batch consistently. A formulation partner can help you weigh cost, skin feel, and claim support before you lock the spec.
If you are scoping a private label serum and want to match the hyaluronic acid grade to your target claims, skin feel, and market, a formulation partner can review the brief with you and suggest a blend that fits before you commit to production.