Metformin, a cheap and widely used diabetes drug, might help treat vitiligo by calming the immune system and reducing oxidative stress — two things that seem to drive pigment loss. A clinical trial was planned but withdrawn before it started, so there’s no hard data yet. It’s not a treatment (yet), but researchers haven’t given up on the idea. One to watch.

1. What is metformin, and why are people talking about it for vitiligo?

Metformin is one of the world’s most commonly prescribed drugs for type 2 diabetes. It helps control blood sugar and improve insulin sensitivity. But here’s the twist: researchers are starting to think it might also help with autoimmune conditions like vitiligo.

How? Turns out metformin isn’t just a glucose regulator — it also seems to calm down certain overactive immune cells (especially the CD8+ T cells that go after pigment-producing melanocytes) and reduce oxidative stress in the body. Both of these are thought to play key roles in vitiligo.

2. Are there any clinical trials testing this idea?

There was a Phase 2 clinical trial planned (NCT05607316) to explore whether oral metformin could safely treat adults with stable vitiligo, starting on 500 mg twice a day and increasing to 1,000 mg twice daily if they tolerate it well. But that trial was withdrawn before enrolling any participants, so no results are available and no active studies are ongoing at this time.

3. How exactly might metformin help treat vitiligo?

It appears to be associated with a reduced risk of incident vitiligo.(1) But so far, most of the promising signs come from lab experiments and mouse models. These studies suggest metformin might:

• Tweak how immune cells like T cells use energy, which in turn dampens their attack on melanocytes.
• Lower oxidative stress — another known trigger in vitiligo.
• Interfere with melanin production and melanocyte structure. While that may sound like it would worsen depigmentation, in autoimmune conditions, the overall effect might actually help protect or restore pigment. 

The science isn’t fully settled, but the dual immune-and-metabolic angle makes this drug particularly interesting.

4. Does it actually work?

Right now, we don’t know for sure. There are no published human clinical trial results yet. However, some mouse studies have shown reversal of depigmentation, and big data sets suggest people with diabetes who take metformin may be slightly less likely to develop vitiligo.(1) Still, that’s far from conclusive — so we’re waiting on solid human data.

5. Is metformin used topically or just taken as a pill?

For vitiligo, it’s only being tested in pill form. There are a few exploratory studies looking at topical metformin for other skin conditions like melasma, but not for vitiligo. If it works, oral delivery seems to be the likely route — at least for now.

6. What about side effects — is it safe if I’m not diabetic?

Generally, yes — but it’s not a free pass. Metformin is well-tolerated by most people, but it can cause some unpleasant GI issues (think nausea, bloating, or diarrhea). It also has a rare risk of lactic acidosis, especially in people with kidney or liver problems. And if you take it long-term, you’ll want to watch your B12 levels.

This is definitely not something to self-prescribe. Start low, go slow, and only with medical supervision.

7. Does metformin affect pigment in other conditions too?

Funny you ask — yes, it does. Metformin has been studied in melasma (a condition with too much pigment), and it seems to help reduce hyperpigmentation. That might sound confusing, but remember: it’s not about painting the skin darker or lighter. It’s about influencing deeper processes like inflammation, oxidative stress, and how skin cells behave under immune pressure. In vitiligo, it may help create a more stable environment for repigmentation to occur.

8. Is it approved for vitiligo?

Nope. Not yet. Metformin is currently being studied as an off-label, investigational therapy. Until there are published results and official guidelines, it should only be considered in the context of clinical research — not as a DIY treatment.

9. Who can participate in the trials?

The withdrawn trial was open to adults with stable vitiligo — meaning no new or expanding spots in the past year. If it gets back on track, you’ll also need to meet other health criteria: no diabetes, no kidney or liver disease, not pregnant, and not currently using phototherapy or immunosuppressive treatments.

10. What’s next for metformin in vitiligo?

The big thing to watch for is the outcome of future clinical trials: does metformin actually help bring pigment back? Researchers will also be looking at immune biomarkers — clues in the blood and skin that tell us how the drug is working under the hood.

If results are promising, next steps might include:

• Combining metformin with other therapies like phototherapy or antioxidants.
• Studying whether it works better in certain patient groups.
• Digging deeper into the science of how it interacts with melanocytes and immune pathways.
   

Summary

Metformin is a low-cost, familiar medication that’s showing early promise as a novel approach to vitiligo. Its ability to calm down rogue immune cells and reduce oxidative stress could, in theory, offer a two-pronged way to protect or restore pigment.

But for now, metformin in vitiligo is more of a “what if” than a “what’s next.” Still, with its unique mix of immune and metabolic effects, it’s one worth keeping an eye on — if future studies decide to pick up the thread.

— Yan Valle

CEO, Vitiligo Research Foundation | Author, A No-Nonsense Guide to Vitiligo

Suggested reading: 

• Acral Vitiligo and Platelet-Rich Plasma: Your Questions Answered
• Topical Treatments for Vitiligo: What We Know (and Still Don’t) About Their Safety
• Could These 3 Proteins Be the Key to Beating Vitiligo?