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Gleam’s teeth whitening strips worked in less than a week – and they’re a third off now

Food stains, be gone

My teeth are definitely whiter thanks to this sub-£25 kit (Gleam/iStock/The Independent)

If, like me, you’ve watched your fair share of American sitcoms, then you’ll notice one thing all the actors – from Zooey Deschanel to Matt LeBlanc – have in common: pearly white teeth. It’s no secret that our neighbours across the pond (or at least the ones in the media) have superior gnashers but, in 2025, it doesn’t have to be that way.

Though regulations on hydrogen peroxide (one of the most popular ingredients in teeth whitening kits) are less strict in the US, it’s still possible to achieve a brilliant smile here in the UK. In fact, I’ve been testing Gleam’s at-home teeth whitening (was £39.99, now £24.99, Gleamteeth.co.uk), and there’s no doubt it’s brightened the ‘ole ivories – but more on that later.

Knowing whether to try a whitening kit, take a professional dentist approach or perhaps give a whitening toothpaste a go can be overwhelming, but I’m here to cut through the noise and offer you a simple and affordable option. Scroll on for my honest Gleam whitening review, plus where to shop for a third off now.

How I tested

The whitening strips sit on the teeth like a clear veil (Lucy Smith)

While Gleam promises “proven results in 30 minutes,” it provides enough strips for 14 sessions. Applying the strips in each sachet as directed (one on the bottom and one on the top row of teeth), I continued to use the treatments daily until I could see a marked difference. In my case, this was around five days, though I proceeded to apply the strips for a further eight days afterwards. I also followed the brand’s advice for its LED kit in terms of whitening prep, brushing my teeth before use and rinsing out with water afterwards. Here’s how I got on.

Why you can trust IndyBest reviews

Lucy Smith has experience of more than five year working across lifestyle, beauty and health. In particular, she’s well-versed on oral health and has written The Independent’s guide to the best teeth whitening kits. When it came to testing Gleam’s teeth whitening kit, she knew which ingredients were (and weren’t) going to work on tough food and drink stains. See her verdict, below.

Gleam teeth whitening strips

gleam teeth whitening review tried and tested indybest

Active ingredients Phthalimidoperoxycaproic acid
Time of day to apply Anytime after brushing
Duration 30-minutes for 14 days max
Sensitivity level None from ingredients, but adhesion on teeth does cause unpleasant pulling sensation upon removal
Time frame for noticeable results Five days
Why we love it
- Stays put for full 30 minute treatment
- No sensitivity
- Affordable
- Whitening noticeable before 14-day cycle completes
Take note
- Those with sensitive teeth will need to be delicate when removing the strips

Currently reduced by more than a third, Gleam’s 14-day treatment offers an affordable alternative to professional (and premium) in-chair dentist whitening, which can often set you back in excess of £1,000 . It’s simple to apply and, as someone who’s tested many a whitening strip in their time, has a superior design. Instead of wrestling with a poker-straight strip over the fiddly, curved surface of your lower teeth, Gleam’s bottom strip is arched with a handy tapered section to fold onto the underside of the teeth.

The strips adhere excellently and I was able to go about my day-to-day tasks – be it tidying or working from home – without fearing the strips dislodging. In fact, I’d argue they adhere a little too well, as I experienced a slight discomfort upon removing them. This process does leave a bumpy residue, but it’s tasteless and disappears quickly after a swill with water or mouthwash.

For the first few days of whitening, I saw little to no improvements, but the changes were – as expected – accumulative. By day five, I could certainly see my teeth looking brighter. For context, I’ve tested more than 10 different whitening treatments over the last few months, so I didn’t expect to see a full yellow to icy white transformation. However, as you can see above, there was a definitive shade lift by the end of my 13-day test.

The most noticeable differences were around the parts of my teeth closest to the gums, where other strips perhaps couldn’t reach. In this way, Gleam deserves praise for its full coverage and effectiveness, reaching even as far as the floss-neglected crevices between my teeth.

The verdict: Gleam teeth whitening strips

On the whole, Gleam’s teeth whitening strips gave my teeth a boosted brilliance – even after many (many) whitening tests prior. They managed to reach the spaces in-between my teeth and showed a noticeable shade lift after just five days, and an even better luminosity after 13. I found the treatment relatively comfortable and easy to perform daily and, with £15 off right now plus an extra 15 per cent with code ‘SUMMER15’, it’s exceptionally good value when compared to competitor products. Bring on the stunning smiles for summer, I say.