A percentage can make a serum feel easy to compare. The larger number looks like a clear winner until you remember that you are buying a finished formula, not an isolated ingredient.
Read the whole product description
Look at the product's intended cosmetic purpose, current ingredient information and application directions. Niacinamide may be one highlighted ingredient among several, and the texture may be as important to your daily experience as the number on the label.
If a percentage is not stated for the exact product, do not borrow one from a similar bottle or a retailer's older listing. Updated formulas and regional versions can make those shortcuts unreliable.
A familiar example
Beauty of Joseon Glow Serum names both propolis and niacinamide. The brand's official page describes a cushiony serum and gives its use directions. That combination of texture, ingredients and method is more informative than selecting from one ingredient alone.
Check what you already use
Read the ingredient information on your existing moisturizer and other leave-on products. If you are adding a dedicated niacinamide serum, be clear about what you want from the new step rather than assuming another bottle is necessary.
Several products can highlight the same ingredient without being duplicates, but repetition should be deliberate. You do not have to collect every category to build a useful routine.
Decide on the finish you want
Consider whether you enjoy a watery serum or a more cushiony layer, and what you will apply afterward. A formula that feels appealing alone may create a different overall finish under moisturizer, sunscreen and makeup.
Choose a manageable size for a first purchase. The lowest price per milliliter is not always the most sensible choice when you have not tried the texture.
Introduce it thoughtfully
Keep other products familiar while assessing the new serum. Follow its directions, and do not assume stinging is evidence of a useful result. Persistent discomfort is a reason to reconsider the formula and seek individual advice.
Explore serums and ampoules, or read our propolis-serum guide if you are comparing a formula that highlights both ingredients.
