What's Behind Your Shedding, From Hormones to Weight Loss Drugs

If you've noticed more hair than usual in the shower drain or on your hairbrush lately, you're probably not imagining it. There are several common hair loss causes, and working out which one applies to you is the first step to fixing it rather than just worrying about it.

Lately, we're hearing one cause more than most. Clients on GLP-1 weight loss medications, things like Ozempic, Wegovy and Mounjaro, are coming in asking the same question “why is my hair falling out, when it never used to?”

The Main Hair Loss Causes

Hair loss usually comes down to one of a few things:

• Hormonal changes
• Stress
• Medication
• Diet

If you're going through menopause or you've recently had a baby, hormones are often the driver, and we've written about both of those in detail (see our guides to menopause and hair thinning and pregnancy hair dos and don'ts). 

By far one of the fastest growing hair loss causes right now sits firmly in the diet category with weight loss, and specifically the kind that comes with GLP-1 medications.

Why Is My Hair Falling Out?

If you're asking yourself ‘why is my hair falling out?’ and you've recently lost a significant amount of weight, especially quickly, that's often your answer. When you eat considerably less than you were before, whether that's from the effects of GLP-1 medication suppressing your appetite or from any other kind of restrictive diet, your body has to make choices about where its limited energy and nutrients go. 

Your body prioritises the vital organs that keep you alive. Hair, for all its importance to how we feel, isn't essential from a survival standpoint, so it tends to lose out on the nutrient distribution in times of restriction. 

Weight Loss Hair Loss

Weight loss hair loss is a real and increasingly common pattern and it's called telogen effluvium. Some types of hair loss damage the follicle itself, the tiny structure under your scalp that hair grows from, which is what makes regrowth difficult or sometimes impossible.

Telogen effluvium doesn't damage the follicle. It simply pushes hair out of its growth phase and into a resting phase. The hair that's affected will eventually shed, but new hair is still there underneath, waiting for the right conditions to start growing again.

It's the most common explanation dermatologists give for this kind of shedding, and it's worth understanding because the outlook is genuinely reassuring. This isn't usually permanent hair loss. It's your body pausing hair growth while it deals with a temporary shortage of nutrients. In short, weight loss hair loss looks alarming but it normally isn't doing any lasting damage.

What The Research Shows for GLP-1 Hair Loss

GLP-1 hair loss has become one of the most common questions we're asked in the salon. Ultimately, less food in, fewer nutrients for hair, more shedding a few months later. Our founder Toni has talked about this on Instagram, walking through why the body treats hair as expendable compared with vital organs when nutrients run short.

This lines up with what the research is starting to show. The American Academy of Dermatology notes that GLP-1 users can experience hair thinning through a combination of stress on the body, nutrient shortfalls and possibly a direct effect of the medication itself, though researchers say more data is still needed to say exactly why. A 2026 systematic review of the evidence found that hair loss is reported more often in people on GLP-1s than in those on a placebo, with the risk climbing when weight loss is fast or substantial. Reported rates of GLP-1 hair loss vary a fair amount between studies, so treat any figures you see, including these, as a snapshot of a fast moving area of research rather than the final word.

The Science Bit, From Karlien Duvenage, Dietitian 

Why does hair loss happen when someone isn't getting sufficient nutrients?

Hair is metabolically expensive to produce and isn't essential for survival, so your body deprioritises it when you don’t have enough energy (calories) to support daily functions after accounting for the energy you burn during exercise. This is often referred to as low energy availability, as it depends on your unique energy needs.

That's why excessive hair loss is one of the signs a clinician looks for when assessing for under-nutrition. What makes it tricky is that it usually shows up 2 to 3 months after changes in intake, so the connection is easy to miss.

What nutrients does hair need most for healthy growth?

The main nutritional driver of hair loss is a reduced total intake, but more specifically, protein. Hair is essentially keratin, a protein. Inadequate energy and protein intake is a well-documented cause of hair loss. Other important nutrients are iron, zinc, calcium, magnesium, potassium, choline, vitamins A, D, E, K, C, and the B-vitamins (particularly B12 and biotin) all matter too. Therefore, on a GLP-1, it's rarely one missing nutrient. It's usually several gaps opening up at once as overall food intake falls.

That's because these medications change a lot about how someone eats. Delayed gastric emptying and appetite suppression are part of how they work, and common side effects such as nausea, vomiting, diarrhoea, constipation, early satiety, and reduced thirst can further chip away at intake. Research shows that energy intake commonly drops by up to ~40%, or around 850 kcal compared with placebo. Some people end up eating less than 800 kcal a day, particularly early in treatment or when GI side effects are pronounced. Food variety narrows too, often with less fruit, vegetables, whole grains and dairy. These are the very foods that supply many of the nutrients mentioned above. Even people who think they're eating more healthily have been found to fall short of important nutrients when assessed professionally.

In addition, many people are already deficient in certain nutrients, such as vitamin D, iron, B12, or zinc, before treatment even begins. So the foundation you start from is often weak, and the gaps become more pronounced. Without guidance, intake can fall quickly enough to cause real problems, including loss of muscle mass and bone density.

Does it matter how fast someone's diet changes, or is it more about how long it goes on for?

It’s both. These medications cause a much sharper drop than most diets, and it happens before someone has time to learn to adjust what they're eating to compensate. The longer that gap continues without support, the more it compounds. Nutrient stores that were fine for a few weeks on lower intake become depleted over months. Which is exactly why early nutritional support matters more than waiting to see how things settle.

What would you tell someone worried about hair loss?

The good news is hair loss itself is reversible. The follicle isn't damaged, just paused, and it starts growing again once intake catches up. That's why I recommend seeing a dietitian before starting one of these medications, not just once a problem appears. Dietitians are well placed to help you meet your protein, iron, and overall nutrient needs while managing a lower appetite or any side effects. If you're already experiencing hair loss, talk to a dietitian to identify what's driving it and get things back on track. Because while hair loss is reversible, many of the other consequences of under-nutrition, like reduced bone density, are not.

Karlien’s References: Almandoz JP, Wadden TA, Tewksbury C et al. Nutritional considerations with anti-obesity medications. Obesity 2024;32:1613-31.

Al-Najim W, Raposo A, BinMowyna MN et al. Unintended consequences of obesity pharmacotherapy: a nutritional approach to ensuring better patient outcomes. Nutrients 2025;17:1934.

Mozaffarian D, Agarwal M, Aggarwal M et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and the Obesity Society. Obesity 2025;33:1475-503.

Will My Hair Grow Back?

For most people, yes. Telogen effluvium is temporary. Once your body is getting the nutrients it needs again, whether that's because your intake has stabilised or your diet has changed, the hair growth cycle tends to return to normal. It's not a quick fix though. Shedding often settles within three to six months, and it can take just as long again to see the regrowth coming through, sometimes longer. Results and timelines vary from person to person, so patience matters here.

What To Do About Weight Loss Hair Loss

If you're on a GLP-1 and worried about your hair, the first step is a conversation with your doctor. From there, nutrition tends to be the biggest lever for weight loss hair loss. 

Losing weight slower, and making sure you're still getting enough protein, fibre and a good mix of whole foods, seems to make a real difference to whether hair loss becomes an issue at all. Going into a GLP-1 with an already poor diet, or cutting corners on nutrition to lose weight faster, is where we tend to see the most noticeable shedding, and where GLP-1 hair loss tends to be at its worst.

On the hair side, this is exactly where a consultation helps. We can't fix a nutrient gap, but we can look at your scalp and the condition of your hair to recommend gentler handling while your hair is more fragile, and help you avoid adding extra damage on top of what's already happening. Products that support the hair you have, rather than promising to reverse the shedding overnight, are usually the right call here.

Book a free consultation here to discuss your next steps. 

Understanding Your Hair Loss Causes

There are many possible hair loss causes, and if yours has started alongside a GLP-1 medication or a significant change in how you're eating, there's a good chance your body is simply reprioritising while it adjusts. 

GLP-1 hair loss and weight loss hair loss are both, for most people, temporary rather than permanent. If you're still asking yourself ‘why is my hair falling out?’ after reading this, or you want a second opinion on what's happening, book a consultation with us and we'll help you figure out what's really going on.