Tranexamic Acid Skincare: The 99-Patient Trial That Matched Hydroquinone, UK Serums From £17 to £93, and Why the Pill Needs a Doctor

In a trial published in Scientific Reports last year, 99 people with melasma were split three ways: a cream with 5% tranexamic acid and 4% niacinamide, a lower-dose encapsulated version of the same pairing, or 4% hydroquinone, the prescription-only lightener dermatologists have treated as the benchmark for forty years. After three months the tranexamic acid groups had moved their pigment scores as far as the hydroquinone group had. The difference was what came with it. The irritation and the rebound turned up on the hydroquinone side, not theirs.

That’s a useful result to have in your pocket when you’re standing in Boots looking at a £17 bottle. It’s also easy to over-read, and most of the tranexamic acid skincare content online does exactly that. So this is the long version: what the ingredient is, what the trials show and don’t, which UK serums earn their price (not the £93 one), how to use it so it stands a chance, and why the tablet version that keeps turning up on TikTok is a conversation with a doctor rather than a shopping decision.

A bleeding drug that wandered into pigmentation clinics

Tranexamic acid is a synthetic cousin of the amino acid lysine. On the NHS it’s prescribed for heavy periods, nosebleeds and bleeding after surgery, and it works by blocking plasmin, the enzyme that breaks clots down. The skin connection was spotted by accident in Japan in the late 1970s, when patients taking it for other reasons came back with lighter, more even faces. Nobody had been looking for that.

The mechanism turned out to make sense. UV light ramps up plasmin activity in keratinocytes, the cells that make up most of your epidermis, and plasmin releases the messengers (arachidonic acid, alpha-melanocyte-stimulating hormone) that tell the melanocytes underneath to make more pigment. It also nudges up the growth factors that build the tiny blood vessels inside a melasma patch, which is why those patches so often carry a faint redness under the brown. Tranexamic acid sits on the plasmin switch. DermNet’s summary, written by a consultant at Guy’s and St Thomas’, lists shrinking that dermal vasculature and damping tyrosinase alongside the keratinocyte-melanocyte effect.

Two things follow. It quietens the pigment signal and the vascular signal at the same time, which almost nothing else on the shelf does. And it isn’t an exfoliant. The word “acid” does a lot of misleading here – The Inkey List’s serum sits at a pH of 6.5 to 7, about the same as tap water. It doesn’t sting, it doesn’t peel, and it doesn’t need “buffering” the way glycolic does.

The trial that matters, and what it can’t tell you

The 2025 study is the one to remember because it’s randomised, double-blind, and compares tranexamic acid with the actual standard of care rather than with a placebo. Ninety-nine patients, three arms, three months, five dermatologist visits. Melanin index and modified MASI scores (the standard melasma severity measure) fell in all three groups. The authors’ conclusion was blunt: the tranexamic acid and niacinamide creams “are as effective as HQ 4% cream”, and with fewer adverse reactions “would be better choices”. The paper is open access if you want the tables.

Now the limits, because they matter. It ran in Iran, on mostly darker skin types – a fair match for the people melasma hits hardest, but not for everyone reading this. Three months is where it stopped, so it says nothing about year two. The 5% cream was made up for the trial and paired with 4% niacinamide, which is not the same product as a 2% serum with acai in it. And the older evidence for topical tranexamic acid is a patchwork of small studies, a lot of them split-face, several comparing 3% tranexamic acid with 3% hydroquinone and calling it a draw. A 2024 network meta-analysis in the Journal of Cosmetic Dermatology tried to rank the different routes and found the combination approaches came out on top, which is roughly what you’d expect.

So: a real effect, moderate in size, with a decent safety record and thin long-term data. That’s a better evidence base than most of what sits in the “brightening” aisle. It isn’t a cure, and the British Association of Dermatologists’ melasma page is clear that nothing is: the condition tends to come back when treatment stops, whatever the treatment.

Four things people repeat about tranexamic acid that aren’t quite right

“Studies show 89% success.” The figure is real, but it comes from a 2016 review of 561 patients in Singapore taking the oral tablet, mostly on top of their existing creams, with no control group. It gets pasted onto serum listings as though a 2% gel did it. It didn’t. An earlier version of this article repeated that mistake; it’s been corrected.

“Higher percentage, faster results.” In the trial above, the 2% encapsulated cream did as well as the 5% conventional one. Delivery and pairing matter more than the headline number. Above 5% you’re in territory nobody has tested on faces for months at a time.

“You’ll see a difference in four weeks.” Inkey’s own product page says four weeks on the banner and six to eight in the FAQ. The trials measured at eight and twelve. Take the FAQ figure. Anyone whose dark spot vanished in a fortnight had a very superficial mark, or is selling something.

“It’s the melasma pill, just weaker.” No. The tablet is a prescription medicine with a screening conversation attached. More on that further down, because it’s the part that matters most.

The UK serums, compared

These are the prices I found in the third week of September. Space NK runs 20% off so often that its sticker price is more of a suggestion.

Product	Tranexamic acid	Paired with	Price	Verdict
The Inkey List Tranexamic Acid Serum, 30ml	2%	2% acai, 2% vitamin C derivative (magnesium ascorbyl phosphate)	£17 at Boots, Inkey, Space NK, Cult Beauty	The one to start with. Fragrance-free gel that layers under anything. The pump is temperamental – a recurring complaint across its 300-odd reviews.
Good Molecules Discoloration Correcting Serum	3%	4% niacinamide	Cheaper than Inkey when it’s in stock, which is not always	The closest thing on the high street to the trial formula. Plainer texture, no frills.
Paula’s Choice Clinical Discoloration Repair Serum, 30ml	3%	5% niacinamide, 0.5% bakuchiol, vitamin E, milk thistle	£55 direct; £52 at Space NK (£41.60 on offer when I checked)	The best-built formula here. The step up if the £17 has stalled at week twelve.
SkinCeuticals Discoloration Defense, 30ml	3%	1% kojic acid, 5% niacinamide, 5% HEPES	£78 to £100 depending on the clinic or retailer	Very good, and priced for the clinic upsell. The HEPES adds mild exfoliation the others lack.
Allies of Skin Tranexamic & Arbutin Advanced Brightening Serum	Not disclosed on the front label	Arbutin and a long list of supporting actives	£93 at Space NK (£74.40 on offer)	Lovely. Also five and a half Inkeys.

Naturium’s 5% Tranexamic Topical Acid is the strongest over-the-counter option I’ve seen in a UK shop (Space NK and Boots both stock the brand) and sits in the same price bracket as Inkey. It’s a reasonable pick if you already know your skin tolerates the ingredient; it’s not the place to start.

My contrarian position is that the money runs out of usefulness somewhere around £55. The clinic-brand serums aren’t five times better than the £17 bottle, because the active is the same molecule at a similar strength and the trials don’t show a dose-response above 3%. What the expensive ones add is a nicer texture and a more considered supporting cast – niacinamide, kojic, arbutin – and you can build most of that yourself for less. If you have £93 to spend on pigmentation, a tinted iron-oxide SPF and a year’s supply of the Inkey will do more than one bottle of anything.

How to use tranexamic acid skincare so it gets a fair trial

Morning, night or both. Inkey says both; the older “Night Treatment” name (dropped in 2022) was about marketing, not chemistry. If you’ll only reliably do one, do the morning, since UV is what flips the plasmin switch in the first place and you’ll be putting SPF over it anyway.

Where it goes. After cleansing and any watery hydrator, before moisturiser. Thin to thick. A pea-sized amount covers the whole face; you don’t need to spot-treat, and the patches you can’t see yet benefit too.

What it likes next to it. Niacinamide, above all – it’s in the trial formula for a reason, and nearly every 3% serum on the table already includes it. A vitamin C serum in the morning is fine underneath (our guide to vitamin C serums for sensitive skin has options that won’t fight it). A retinoid at night is fine too; if you’re choosing one, retinal rather than retinol gets you there faster. Azelaic acid is the natural partner for anyone whose marks are red as much as brown – the azelaic acid guide covers the strengths, and the rosacea-specific piece explains why the two together suit reactive skin. If you like an exfoliating acid, mandelic is the gentle one to pair; just don’t stack a strong glycolic and a retinoid and this on the same evening and then wonder why your cheeks are hot.

Twelve weeks, photographed. Eight is the minimum in the studies; twelve is a fair test. Take a photo on day one by the same window at the same time of morning, no filter, and repeat at week six and week twelve. Your eyes are terrible at judging slow change and your bathroom light is worse. And if nothing has moved by week twelve, stop and see a GP or a dermatologist rather than buying a pricier bottle of the same thing.

The SPF decides whether any of it works. This is the bit that gets a sentence in most guides and deserves a paragraph. Melasma is driven by UV, by visible light and by heat, not just by the burning rays. UVA comes through cloud and through the window of the train. Visible light – the bit a standard SPF doesn’t block – is why melasma sufferers on tinted, iron-oxide sunscreens do better than those on clear ones, and it’s the reason a bare SPF 50 can feel like it’s letting you down. Our daily SPF face cream guide has under-£25 options; the British sunscreen brands round-up includes tinted ones; and if you’ve been relying on the SPF in your moisturiser, this piece explains why that’s been quietly undoing your serum. Heat matters too: hot yoga, standing over a roasting tin, a sauna habit, even the near-infrared warmth from an LED mask pressed against a melasma-prone cheek. None of these are reasons to stop living. They’re reasons not to be baffled when the patch comes back in August.

Don’t stop when it fades. Drop to three or four applications a week rather than to zero. The pigment signal hasn’t gone anywhere; you’ve just been sitting on it.

What it won’t shift

Dermal melasma, where the pigment has dropped into the deeper layer of skin, barely responds to anything you can buy. That’s clinic territory, and even lasers have a habit of making melasma angrier. A dermatologist can tell you which type you have with a Wood’s lamp in about thirty seconds; it’s worth asking before you spend a year on serums.

Red marks aren’t brown marks. The pink-purple ghosts a spot leaves behind on paler skin are post-inflammatory erythema – dilated capillaries, not pigment – and tranexamic acid’s vascular effect helps a little, but time and azelaic acid help more. Freckles won’t budge either, and you wouldn’t want them to. Nor will it outrun a summer of no hat and no sunscreen.

And any patch that has appeared suddenly, sits on one side only, or is changing shape or colour needs a professional look before it needs a serum. Our piece on skin cancer signs covers what to watch for; melanoma can look like a pigmentation problem right up until it doesn’t.

The tablet: read this before you ask a GP for it

Oral tranexamic acid for melasma is 250mg twice a day, usually for three to six months, alongside sunscreen and whatever cream you’re already on. The evidence is stronger than for the serums and the caveats are bigger. In a placebo-controlled trial of 44 people, pigment scores fell by 49% on the tablets against 18% on placebo over three months. In the 561-patient Singapore series, nearly nine in ten improved, responders typically did so within two months, about 7% had side effects (bloating, headaches, lighter periods, the odd bout of numbness), and 27% of those who improved relapsed within months of stopping. One woman developed a deep vein thrombosis and was later found to have an inherited clotting disorder. She should never have been prescribed it, which is precisely what screening is for.

That last point is why this isn’t a shopping decision. Tranexamic acid helps clots persist. The larger cohort studies in melasma patients haven’t found an increased clot rate at these low doses, but they’re too small and too short to rule out a rare one, and the NHS is clear it isn’t suitable for anyone who’s had a clot in a vein or the lungs. A sensible prescriber will also want to know about the combined pill, smoking, family history, pregnancy and long-haul flights. No country has licensed the tablet for melasma; every prescription is off-label.

Dr Amel Ibrahim, a GMC-registered doctor who runs a London prescription-skincare clinic, published a review of the oral evidence in July that’s the most level-headed thing I’ve read on it. Her verdict is that the “melasma pill” hype is overblown: the effect is moderate, the gains mostly fade once the course ends, and the aim with melasma is “control rather than cure”. She also notes the one small head-to-head trial to date found the tablet and the topical did about the same over twelve weeks. So if you’ve never used the serum properly, the tablet is not step one.

One more thing, because it comes up. If you already have tranexamic acid tablets in the cupboard for heavy periods, taking them daily for your face is not the same as taking them for three days a month, and it skips every safety check. Don’t.

Who it suits, who should skip it

It suits the classic hormonal melasma that arrived with pregnancy or the pill and sat on the cheekbones, forehead and upper lip ever since. It suits brown post-spot marks on medium and darker skin, which is where the studies are strongest. It suits anyone who’s tried hydroquinone or high-strength acids and found their face couldn’t take it – sensitive, rosacea-prone skin tolerates this in a way it tolerates almost nothing else in the category. And it suits people who want one thing they can use every day for a year without a break week, which is how pigmentation is actually managed.

Think twice if you’re pregnant or breastfeeding. Inkey labels its serum as safe for both, and topical use is probably fine, but “probably” is the honest word – the pregnancy data is thin, and azelaic acid has a longer track record if you’d rather. Skip it for now if your barrier is wrecked; get the flaking and stinging under control first (our barrier repair routine is a good template even outside pollen season), because nothing brightening works on a barrier that’s letting everything in. Skip it if your marks are red rather than brown. And skip it if you want a result by the end of the month – this is a January-to-April project, not a weekend one.

It’s also worth knowing that melasma often flares or first appears around perimenopause, so if the patches arrived in your late forties with the hot flushes, our menopause skincare guide covers the wider picture. And if you’ve been eyeing the glutathione supplements sold for the same problem, read that first; the evidence there is a good deal weaker than for a £17 gel.

Start this week and the checkpoint is mid-December: the same window, the same time of morning, the same unfiltered photo. If the patch is lighter, keep going and drop to maintenance in the spring. If it isn’t, you’ve spent £17 and learned something a dermatologist can now use. If blackheads are the concern rather than pigmentation, start with salicylic acid instead.