# COSRX Hydrium Ampoule vs HA 3 Serum

**Question answered:** Should I choose COSRX Hydrium Triple Hyaluronic Moisture Ampoule or The Hyaluronic Acid 3 Serum?

**Short answer:** Choose Hydrium Triple Hyaluronic Moisture Ampoule if you want a short, 15-ingredient hydrating ampoule with three forms of hyaluronic acid, panthenol and gentle PHAs. Choose The Hyaluronic Acid 3 Serum if you want a stated 3% sodium hyaluronate plus natural moisturizing factors, amino acids and ceramide NP. Both are sold as fragrance free, and both list mild acids.

By Nora Ellison. Published 2026-10-29. Data is taken from manufacturer labels; the products have not been tested.

## What this means for you

### Start with what you notice

Both are COSRX hydrating serums for dry or dehydrated skin. The difference is what comes with the hyaluronic acid.

### The ingredient names, translated

Hyaluronic acid holds water in the top layer of skin. The Hydrium ampoule pairs three hyaluronic acid forms with panthenol and two polyhydroxy acids (PHAs), which exfoliate gently. The 3% serum states its sodium hyaluronate strength and adds sodium PCA, amino acids, ceramide NP and cholesterol, plus small amounts of lactic and citric acid. A stated percentage doesn't prove a more hydrating finished product.

### How to decide

- Want a short ingredient list with panthenol and PHAs? Hydrium Triple Hyaluronic Moisture Ampoule.
- Want a stated 3% HA with moisturizing factors and ceramide? The Hyaluronic Acid 3 Serum.
- Very sensitive to acids? Patch test either; both list mild acids.

### What to expect

Either should make skin feel softer and more comfortable under moisturizer. Neither treats a skin condition. We haven't tested either product.

General guidance, not a test of these products: [How hydrating ingredients work](https://pmc.ncbi.nlm.nih.gov/articles/PMC4885180/); [AAD: dermatologists' tips to relieve dry skin](https://www.aad.org/public/everyday-care/skin-care-basics/dry/dermatologists-tips-relieve-dry-skin). Each product's label source is linked on its product page.

## Short formula vs long formula

[COSRX Hydrium Triple Hyaluronic Moisture Ampoule](product:cosrx-hydrium-triple-hyaluronic-moisture-ampoule) lists 15 ingredients: glycerin and glycols, sodium hyaluronate, [hyaluronic acid](/ingredients/hyaluronic-acid/), hydrolyzed hyaluronic acid, [panthenol](/ingredients/panthenol/), gluconolactone and lactobionic acid. COSRX describes a viscous texture with a non-greasy finish.

[COSRX The Hyaluronic Acid 3 Serum](product:cosrx-the-hyaluronic-acid-3-serum) is a 20 mL serum with 3% sodium hyaluronate. Its 43-ingredient list includes betaine, sodium PCA, sodium lactate, amino acids such as serine and glycine, and ceramide NP with cholesterol.

> **Skin Realist check:** if your skin is happy with one, there's no prize for owning both.

## Label differences worth knowing

The 3% serum also lists alcohol, low on the list. Neither lists fragrance or essential oils. See our [COSRX HA essence vs Hydrium ampoule comparison](/comparisons/cosrx-hyaluronic-acid-essence-vs-hydrium-ampoule/) and [glass skin layering guide](/articles/glass-skin-routine-hydration-layering/).

## Manufacturer sources

- [COSRX Hydrium Triple Hyaluronic Moisture Ampoule](https://www.cosrx.com/products/hydrium-triple-hyaluronic-moisture-ampoule)
- [COSRX The Hyaluronic Acid 3 Serum](https://www.cosrx.com/products/the-hyaluronic-acid-3-serum-bundle)

Sources and label-check dates are recorded on the product pages.

| Product | Price | Key ingredients | Skin types | Fragrance | Flagged ingredients | Size | Source | Buy |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| [COSRX Hydrium Triple Hyaluronic Moisture Ampoule](https://dermalguide.com/products/cosrx-hydrium-triple-hyaluronic-moisture-ampoule/) | $20.80 at [Stylevana](https://www.awin1.com/pclick.php?p=43018996001&a=3132625&m=90791) (affiliate), checked 2026-10-29 07:35 UTC | Hyaluronic Acid | Brand doesn't say | Marketed as fragrance free | No flags recorded; not a safety guarantee | 40 ml | [Manufacturer label](https://www.cosrx.com/products/hydrium-triple-hyaluronic-moisture-ampoule), checked 2026-10-10 | [Amazon (affiliate)](https://amzn.to/4zuV6iM) |
| [COSRX The Hyaluronic Acid 3 Serum](https://dermalguide.com/products/cosrx-the-hyaluronic-acid-3-serum/) | $20.00 at [Stylevana](https://www.awin1.com/pclick.php?p=43018986386&a=3132625&m=90791) (affiliate), checked 2026-10-29 07:35 UTC | Hyaluronic Acid 3% | Brand doesn't say | Marketed as fragrance free | Alcohol | 20 ml | [Manufacturer label](https://www.cosrx.com/products/the-hyaluronic-acid-3-serum-bundle), checked 2026-10-10 | [Amazon (affiliate)](https://amzn.to/4rYGIg1) |

## Which to choose

Consider COSRX Hydrium Triple Hyaluronic Moisture Ampoule when: You want a short, 15-ingredient ampoule with panthenol; You like the idea of gentle PHAs in a hydrating step.

Consider COSRX The Hyaluronic Acid 3 Serum when: You want a stated 3% sodium hyaluronate; You want amino acids, sodium PCA and ceramide NP in the formula.


## Questions

### Which states its hyaluronic acid percentage?

The Hyaluronic Acid 3 Serum states 3% sodium hyaluronate. The Hydrium ampoule doesn't state a percentage.

### Do they contain acids?

The Hydrium ampoule lists gluconolactone and lactobionic acid. The 3% serum lists lactic acid and citric acid.

### What sizes are they?

COSRX lists the Hydrium ampoule at 40 mL and The Hyaluronic Acid 3 Serum at 20 mL.