Can You Use Niacinamide and Vitamin C Together?

"Can I use Niacinamide and Vitamin C together?" is one of the most searched skincare questions on the internet. The answer has been debated, misunderstood, and oversimplified — and a lot of the advice floating around online is either outdated or just wrong.

Here is a clear, definitive answer.

The short answer

It depends on which form of Vitamin C you're using.

Pure Vitamin C (L-Ascorbic Acid): Do not use it in the same routine as Niacinamide. Keep them separated — Niacinamide in the AM, pure Vitamin C in the PM.
Vitamin C derivatives (Ascorbyl Glucoside, Magnesium Ascorbyl Phosphate, Ascorbyl Tetraisopalmitate): Still avoid using them alongside Niacinamide in the same routine, but the reaction is gentler and less of a concern at lower concentrations.

Why they conflict

The pure Vitamin C + Niacinamide reaction

Pure L-Ascorbic Acid is highly acidic (optimal pH 2.5–3.5). Niacinamide is a form of Vitamin B3 that works at a higher pH. When they meet on the skin, two things can happen:

Reduced efficacy for both. The acidic environment of Vitamin C can convert Niacinamide into nicotinic acid. Nicotinic acid is not harmful, but it doesn't deliver the same benefits as Niacinamide.
Flushing and redness. Nicotinic acid is a vasodilator — it can cause temporary facial flushing in some people, particularly at higher concentrations of both ingredients.

The reaction is not dangerous, but it does waste the products and can cause visible redness. Given how easy it is to simply use them in separate routines, there's no good reason to risk it.

Why EUK 134 is an even stricter concern

While this post focuses on Niacinamide, it's worth mentioning that pure Vitamin C has an even stricter conflict with EUK 134 0.1%. EUK 134 is an antioxidant enzyme catalyst — and strong acids (including L-Ascorbic Acid) structurally destroy it. These two must be kept in entirely separate routines without exception.

The case for Vitamin C derivatives

If you want to use both Vitamin C and Niacinamide in your routine without any hassle, switching to a Vitamin C derivative is the most practical solution.

Derivative forms of Vitamin C — such as:

Ascorbyl Glucoside Solution 12% (The Ordinary)
Magnesium Ascorbyl Phosphate 10% (The Ordinary)
Ascorbyl Tetraisopalmitate Solution 20% in Vitamin F (The Ordinary)

...are converted to active Vitamin C in the skin after absorption. They are significantly more stable than pure L-Ascorbic Acid, work at a higher, gentler pH, and have a much shorter conflict list.

Ascorbyl Glucoside, for example, only formally conflicts with Niacinamide. That's it — no issues with Peptides, EUK 134, Retinoids, or Copper Peptides. Many skincare formulators and dermatologists consider Ascorbyl Glucoside the gold-standard derivative precisely because of this flexibility.

Even with derivatives, it is worth keeping them in separate routines from Niacinamide where possible — but the consequences of accidental overlap are far less significant than with pure Vitamin C.

The recommended solution: AM and PM split

DECIEM (the parent company of The Ordinary) recommends the following split, and the Skincare Routine app applies this automatically when you add both products:

Routine	Products
AM	Niacinamide 10% + Zinc 1%
PM	Pure Vitamin C product

This gives each ingredient the full, uncompromised routine it needs. Niacinamide is an excellent AM ingredient — it controls sebum, minimises pores, and brightens. Pure Vitamin C performs well in the PM, away from UV light and away from morning actives it would conflict with.

If you use a derivative Vitamin C, you have more flexibility:

Routine	Products
AM	Derivative Vitamin C (e.g. Ascorbyl Glucoside 12%)
PM	Niacinamide (if needed in PM, though AM is more typical)

Or simply use Ascorbyl Glucoside in the AM and Niacinamide in the AM — on separate product slots, layered correctly — since the derivative conflict with Niacinamide is mild enough that many users tolerate it without issue.

What about layering order?

If you are keeping them in separate routines (as recommended), layering order between these two specific ingredients is not a concern. But for general context:

Niacinamide (water-based serum) applies after toner/essence and before oils and moisturiser.
Vitamin C serums (depending on water or oil-based) also apply at the serum stage — water-based first, oil-based after.

Within the same routine, never layer directly: apply water-based products from thinnest to thickest and allow each to absorb before the next.

How the Skincare Routine app handles this automatically

You do not need to memorise any of this if you use the Skincare Routine app.

When you add both Niacinamide 10% + Zinc 1% and a pure Vitamin C product to your routine, the app automatically places Niacinamide in the AM and Vitamin C in the PM — following DECIEM's own recommendation.

During your routine, if you tick Niacinamide and then approach a pure Vitamin C product:

A red checkbox flags the conflict
The reason is shown inline: the products shouldn't be used in the same session

If you instead add Ascorbyl Glucoside (a derivative), the app correctly reflects the lighter conflict status for that product — distinguishing between the behaviour of pure and derivative forms automatically.

The app is available on iOS and Android at skincareroutine.app.

Summary

Pure Vitamin C + Niacinamide: Avoid using together. Keep Niacinamide in AM, pure Vitamin C in PM.
Derivative Vitamin C + Niacinamide: A lower-level conflict. Separation is still preferred but the consequences of overlap are much less significant.
The simplest fix: Switch to Ascorbyl Glucoside Solution 12% as your Vitamin C — it's effective, stable, and has a much shorter conflict list.
The easiest solution overall: Use the Skincare Routine app and let it manage the separation automatically.