Retinoids, Explained: Which Vitamin A, and Why Percentage Is Not the Whole Story
"What percentage retinol should I be using?" is one of the questions I am asked most often, in clinic and online. It is a good question, but it is the second question. The first question is: which form of vitamin A is actually in the product?
That distinction matters more than the number on the box. Two products can both say "retinol", both state a percentage, and behave quite differently on your skin. Here is why, in plain English.
What "Retinoid" Actually Means
Retinoid is the umbrella term for vitamin A and every derivative of it used in skincare. Retinol is the family member most people can name, but it is only one of them. Retinyl palmitate, retinaldehyde and retinoic acid are all retinoids too, and they are not interchangeable.
Here is the part most people are never told. Your skin can only use one of them directly: retinoic acid. The receptors in your skin that respond to vitamin A respond to that form. Every other retinoid has to be converted by your skin's own enzymes, step by step, before it can do anything at all.
So the real difference between retinoids is how many conversion steps sit between what is in the jar and the form your skin actually uses.
The Conversion Ladder
Imagine vitamin A as a ladder. At the bottom sits retinoic acid, the active form. Each rung above it is one conversion step your skin has to perform:
Retinyl esters (such as retinyl palmitate) → retinol → retinaldehyde → retinoic acid
Each arrow is work your skin does. As a general rule, the further a form sits from the bottom of the ladder, the gentler and less immediately available it tends to be, because the conversion steps limit how much active vitamin A arrives, and how fast. The closer a form sits to retinoic acid, the more directly available it tends to be, and the more care the product needs in how it is introduced.
This ladder, not the percentage on the front of the pack, is what mostly determines how a vitamin A product behaves on your skin.
The Four Forms You Will Actually Meet
Retinyl palmitate is an ester, the gentlest rung and the furthest from the active form. You will find it in many high-street creams, often listed simply as "vitamin A". There is nothing wrong with it. It is the shallow end of the pool: well tolerated, and correspondingly modest in what it can achieve for most people.
Retinol is the household name, two conversion steps from the active form. It is also one of the most studied ingredients in skincare, with a substantial body of research supporting its role in improving the appearance of fine lines, texture and skin tone over time. The important nuance: the percentage on the jar tells you how much retinol the product contains, not how much retinoic acid your skin ends up with.
Retinaldehyde, often shortened to "retinal", sits one step from the bottom. Because it needs only a single conversion, it can act more readily than retinol at comparable concentrations. It was historically harder to keep stable in a bottle, which is why it is less familiar, but modern formulations have largely solved that, and it is appearing on more shelves each year.
Retinoic acid, also known as tretinoin, is the active form itself. No conversion needed. In the UK it is a prescription-only medicine, and I think that classification is sensible rather than restrictive: it is not simply "the strongest cosmetic on the shelf", it is a medicine that should be chosen with a prescriber who has weighed your skin history, your goals and how your skin is likely to tolerate it. If a prescription retinoid ever becomes appropriate for you, that is a conversation in a consultation, not a shopping decision.
Why the Percentage Question Misleads
Now the marketing problem. Products are sold on a percentage because a number is easy to compare and easy to make sound impressive. Three things make that number a poor guide on its own.
1. Percentages of different forms are not comparable. 1% retinyl palmitate, 0.3% retinol and 0.05% retinaldehyde are not three settings of the same dial. They sit on different rungs of the ladder, and your skin has to do different amounts of work to reach the active form from each. A product can quote an impressive-sounding percentage of a form that sits high on the ladder, while delivering less available vitamin A than a modest percentage of a form nearer the bottom.
2. The formulation decides what actually arrives. Retinoids are unstable ingredients that degrade with light, air and time. How well a product is stabilised, whether the retinoid is encapsulated for slow release, the base it sits in and the ingredients around it all change what reaches your skin and how quickly. Two products with the same retinol percentage can genuinely behave differently.
3. Chasing percentage mostly buys irritation. The strongest product is not the one with the biggest number, it is the one your skin is still happily using six months from now. Jumping to a high strength early mainly increases the adjustment reaction, and irritation is the single biggest reason people give up on vitamin A entirely. I wrote in my piece on moisturisers that patients often stop retinol within a fortnight because their skin feels dry or flaky while it adapts. They never reach the stage where it starts to genuinely help, because the discomfort felt like failure. It is not failure. It is usually just too much, too fast.
What the Adjustment Phase Actually Means
Some dryness, flaking or tightness in the first weeks of a retinoid is normal adaptation, not a sign the product is wrong for you. Some people also notice a brief phase of breakouts as cell turnover speeds up; for most people this settles within a few weeks to a couple of months.
The way through is gradual, and this is how I plan it with patients:
- Start low and slow. The gentlest sensible form and strength, two nights a week to begin, building frequency over weeks as your skin accepts each step.
- Use a moisturiser strategically, not habitually. This is where a moisturiser earns its place: as a planned buffer during retinoid adaptation, layered where and when your skin needs backup, rather than a daily dependency. It is a tool for this transition, not the goal.
- Protect every morning. Vitamin A can make skin more sun-sensitive, so daily SPF is not optional while you use it.
- Know when to stop. Persistent pain, swelling, or a widespread rash is not adaptation. Stop and seek advice. And if you are pregnant, planning pregnancy or breastfeeding, vitamin A products are generally not recommended: speak to your doctor or midwife before using any, including over-the-counter ones.
How I Choose the Right Form in Clinic
There is no universal "best retinoid". The right form depends on your skin's history, what you have already tried, what you want to change, and how much resilience your barrier currently has. The results-led approach I trained in, developed by the dermatologist Dr Zein Obagi, treats vitamin A as the cornerstone of skin renewal and introduces it progressively, at the pace your skin accepts, with the goal of long-term function rather than short-term comfort.
In practice that often means starting with a well-formulated cosmetic retinol, then selecting and adjusting strength and formulation according to what your skin needs and currently tolerates, and I tell every patient exactly how and when to use what they take home. The seven vitamin A products in my current Obagi catalogue cover retinol in two strengths, Obagi Retinol 0.5% and 1.0%, the Obagi Retinol + PHA Refining Night Cream as a gentler entry point, and tretinoin in three strengths, with the 0.05% also available as a gel. From ZO Skin Health I use two retinols: Wrinkle + Texture Repair, a 0.5% retinol emulsion, and Radical Night Retinol at 1% retinol. Two brands can put the same percentage on the label in very different formulations, so choosing between them is a formulation question, not a strength race. The tretinoin products are prescription-only medicines, chosen in consultation rather than off a shelf.
Frequently asked questions
Is retinol the same as a retinoid?
Retinol is one member of the retinoid family. All retinoids are forms of, or derivatives of, vitamin A: retinol, retinaldehyde, retinyl palmitate and retinoic acid are all retinoids. Products that say "retinoid" on the box usually contain one specific form, and which one matters.
What percentage retinol should I start with?
It is the wrong first question, and I say that as the person patients ask it of. Choose the form and the formulation first, then start at the lowest strength your skin tolerates while you build up frequency. A modest concentration used consistently for six months will outperform a maximum strength abandoned in a fortnight.
My skin is sensitive. Are retinoids off the table?
It depends why your skin is sensitive. Skin that has become reactive through years of over-protection often benefits from carefully introduced vitamin A as part of rebuilding its resilience, which is the pattern I describe in my guide to moisturiser dependence. Skin with an underlying condition such as rosacea or eczema needs a more cautious, medically-informed plan, and that is exactly what a consultation is for.
Do I need a prescription retinoid?
Most skin goals can start with well-formulated cosmetic retinoids used properly. Prescription-strength retinoic acid is a medicine, and if it is ever appropriate for you it should come from a prescriber who has assessed your skin, not from a strength-chasing instinct. If you are wondering which camp you fall into, that is a fair question to bring to a first consultation.
The order of the questions matters more than any single answer: form first, formulation second, percentage last. If you would like a vitamin A plan built around your skin rather than a number on a jar, book a skin consultation and we will work out where to start, and how to adjust it as your skin responds.