We Review Medik8 20 Retinal Serum & Share Where You Should Start
Eagle-eyed readers will have noticed that Medik8 use the term ‘retinal’ rather than ‘retinol’. Both are forms of vitamin A, but retinal is a superior version as it requires fewer conversions. If you'd like to know more, read our beginners guide to retinol next.
Medik8’s Crystal Retinal formulas start from Crystal Retinal 1, which contains 0.01% retinaldehyde, and gradually increase up to Crystal Retinal 24, which includes a more potent 0.24% dose of retinaldehyde. At Space NK, however, we stock up to Crystal Retinal 20, containing 0.2% retinaldehyde. Unsure where to begin? Scroll to the end where we break down each strength and help you find the best retinol serum for your skin.
But first, let’s take a closer look at Medik8’s second-strongest formula, Crystal Retinal 20, to see just how potent it really is…
Shannon’s Medik8 Crystal Retinal 20 Serum review
• Skin type: Combination
• The product: Medik8 Crystal Retinal 20, £99.00

I’m in the process of deciding whether to experiment with ‘tweakments’, it’s currently unchartered territory for me. Up until now, I’ve been relying on vitamin A to help curb the signs of ageing and I’ve been working my way up Medik8’s Crystal Retinal ladder. I’ve used the 6 and 10 formulas, so I was ready for the 20. Prior to reviewing, I was using Murad Retinal ReSculpt Overnight Treatment, £59.00 which I enjoyed.
I’m going to be completely honest, I expected some initial irritation given that the Crystal Retinal 20 is twice the potency of the 10, but I had zero issues. It goes on quite thick and does take a while to absorb, but trust me, the results warrant the wait time!
I didn’t notice any immediate changes – you rarely do with vitamin A, but after two weeks I definitely felt a difference in the firmness and clarity of my skin. My morning moisturiser goes on more easily too, so it’s had an impact on my skin texture.
While I used Medik8’s Crystal Retinal 20 every other day, I recommend introducing it gradually if you haven’t used a strong vitamin A previously. It goes without saying if you’re a skincare lover, but make sure you wear SPF the following day too!
Lynn’s Medik8 Crystal Retinal 20 Serum review
• Skin type: Combination and menopausal
• The product: Medik8 Crystal Retinal 20, £99.00
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I’m fully signed up to Medik8’s Crystal Retinal range and the Medik8 Crystal Retinal Ceramide Eye 6, £55.00 and Medik8 Crystal Retinal 10, £89.00 are firm fixtures in my skincare routine. I usually apply them twice a week, or every three days in the evening.
Like Shannon, I expected some tingling or redness, but I didn’t experience either. What was different to Medik8’s 10 was the opacity. No matter how early I applied it in the evenings, it still transferred onto my pillowcase.
While the photos don’t do the results justice, I’ve definitely found my skin looks plumper and more even over the last couple of days. I’ve only been using Medik8 Crystal Retinal 20 for a couple of weeks, so I need to use it for at least another month to see the longer term benefits – I’m impressed so far though.
Hanitra’s Medik8 Crystal Retinal 20 Serum review
• Skin type: Oily and acne-prone
• The product: Medik8 Crystal Retinal 20, £99.00

I’ve been using a retinol serum regularly in my skincare routine for about two years now as I struggle with acne and acne scarring. Vitamin A, particularly retinal, has been a key ingredient to help fade my pigmentation marks. While I have used Medik8’s Crystal Retinal range before, I’ve only ever made it up to 6 so I was slightly apprehensive about jumping to 20.
My skin didn’t react with any irritation, however I want to stress that I did do a patch test and I highly recommend you do one too! If you’re familiar with Medik8’s retinal serums, you’ll know they have more of a cream like texture than serum. This is a bonus for me as I feel like it gives you slightly more control with where you’re applying it and how much. I like to focus on my cheeks as that’s where I have the most pigmentation.
While I definitely need to use the Crystal Retinal 20 for longer, I have noticed a difference across my forehead. Within a few days, my forehead felt and looked much smoother. I’ve been using this retinoid serum once a week due to its strength but might consider upping this to twice a week in the autumn.
The verdict on Medik8 Crystal Retinal 20 Serum
Despite only using the new Medik8 Crystal Retinal 20, £99.00 for a few weeks, all three testers will continue to use the formula. It’s worth noting that all three had used vitamin A prior to using this potent formula and Hanitra, who had the least experience, did a patch test. We highly recommend doing a patch test with any vitamin A product!
The pros: While the formula contains 0.2% retinaldehyde, Medik8 have ensured that this serum doesn’t leave your skin feeling dry, irritated or stripped. All three testers noted a change in how their skin looked and felt within just a couple of weeks.
The cons: This formula is much thicker than other vitamin A products, so it takes a while to sink in. For Lynn, the product transferred onto her pillowcase too!
Which Crystal Retinal Strength Is Right For You?
Medik8
Crystal Retinal 1, £45.00
For Sensitive Skin
Crystal Retinal 1 is ideal for anyone with sensitive or reactive skin who wants to take things slowly. With 0.01% retinal and a host of soothing, hydrating ingredients, it provides an effective yet low-strength introduction, making it perfect for those feeling cautious about trying vitamin A.

Medik8
Crystal Retinal 3, £50.00
For Beginners
If you don’t consider your skin sensitive, Medik8 recommends starting with Crystal Retinal 3. With 0.03% retinal, it’s suitable for most vitamin A beginners - just remember to introduce it gradually, as with all vitamin A products.

Medik8
Crystal Retinal 6, £69.00
For Moderate Users
Crystal Retinal 6 is designed for those who have completed a full tube of Crystal Retinal 3 or have been using a low-strength vitamin A for 8–12 weeks. With 0.06% retinal, it’s for anyone already comfortable with vitamin A who wants to take the next step.

Medik8
Crystal Retinal 10, £89.00
For Advanced Users
Similarly, if you’ve comfortably finished a full tube of Crystal Retinal 6 and your skin is fully adjusted, you’re ready for Crystal Retinal 10. With 0.1% retinal, it delivers a stronger dose to take your results to the next level.

Medik8
Crystal Retinal 20, £99.00
For Highly Experienced Users
Medik8 recommend only moving on to Crystal Retinal 20 after completing two full tubes of Crystal Retinal 10 - that’s how potent this serum is. With 0.2% retinal, it’s designed for users ready for clinical-strength results.

More from Medik8
The brand’s retinal range might have put it on the map, Medik8’s vitamin C and hyaluronic acid formulas are equally as impressive. Put it this way, if you’re serious about your skincare, Medik8 is absolutely a brand to have not just on your radar, but in your bathroom cabinet. And, if you’re using vitamin A and have experienced any form of dryness, we recommend making a beeline for the brand’s nourishing moisturisers.
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