A major new study says the popular diabetes and weight-loss shots can thin your hair, but the risk is small, and the hair usually grows back.

Millions of people now take drugs like Ozempic, Wegovy, Mounjaro, and Zepbound to manage diabetes or lose weight. Along with the pounds lost, some users say they are losing something else too: their hair. For years, this was mostly word of mouth, shared in online forums and dermatology waiting rooms. Now, a large study out of the University of Pennsylvania, published in one of the world’s most respected medical journals, The BMJ, gives us real numbers. Here is what it found, why it might happen, and what you can do if it happens to you.

What the New Study Found

Researchers looked at health records for nearly 35,000 adults with type 2 diabetes treated at Penn Medicine between 2019 and 2024. About 12,000 of them had started a GLP-1 drug, the class that includes Ozempic, Wegovy, Mounjaro, and Zepbound. The researchers compared these patients to people taking two other common diabetes drugs, known as SGLT-2 inhibitors and DPP-4 inhibitors.

The result: people on GLP-1 drugs were 37 percent more likely to develop hair loss than those on SGLT-2 inhibitors, and 68 percent more likely than those on DPP-4 inhibitors 1,2. That sounds alarming, but the actual numbers remained small. Out of every 1,000 people taking a GLP-1 drug for a year, about 7 developed hair loss. Among those on the other drugs, it was closer to 4 or 5 out of 1,000.

Most of the hair loss was the kind doctors call non-scarring. That is good news because it means the hair follicle itself was not destroyed. It went dormant, not dead, so the hair can usually grow back. The study also found that hair loss showed up within the first year of starting the medication, then leveled off.

This was not the first hint of a problem. Smaller studies had already flagged an increase in hair loss reports tied to semaglutide, the drug in Ozempic and Wegovy, and tirzepatide, the drug in Mounjaro and Zepbound. Those earlier signals were part of why the FDA said in 2023 that it was looking into the issue.

No study is perfect, and this one has real limits worth knowing. It followed patients who were already diagnosed with type 2 diabetes, not people using these drugs purely for weight loss, so results could differ for that larger and growing group of users. The researchers also relied on medical records rather than examining every patient’s scalp in person, which means mild cases that people never mentioned to a doctor were likely missed.

Because this was an observational study, meaning the researchers watched what happened rather than running a controlled experiment, it cannot prove with certainty that the drugs themselves caused the hair loss. It can only show a strong pattern. The research team ran the numbers several ways, including a check for hidden bias, and the pattern held up each time. That kind of consistency makes doctors take a signal seriously.

Why These Drugs Might Cause Hair Loss

The study’s authors, along with outside doctors, do not think the drug itself attacks the hair. The more likely culprit is the weight loss itself. Losing a lot of weight quickly is one of the most common triggers of a condition called telogen effluvium. Hair grows in cycles: growing, resting, and shedding. Normally, 80 to 90 percent of your hair is in the growing phase at any time. A major physical stress, like rapid weight loss, surgery, illness, or even childbirth, can push a large batch of hair into the resting phase all at once. Weeks or months later, that hair falls out, often in noticeable clumps.

Eating less can also mean eating fewer of the nutrients hair needs, such as protein, iron, zinc, and biotin. Cleveland Clinic endocrinologist Dr. Kathy Zhou says the body treats sudden weight loss as a stress and starts protecting vital organs first, hair growth second. She estimates that 25 to 33 percent of people on these drugs notice some hair shedding, a higher number than the study found, likely because many mild cases never make it into a formal diagnosis.

Board-certified dermatologist Dr. Jennifer Holman points out that GLP-1-related hair loss can behave differently than a one-time shock like childbirth. Because the weight loss often continues for months, the hair shedding cycle may keep getting interrupted instead of resetting quickly. Hormone shifts, including changes in thyroid function, may also play a minor role, though the study’s researchers say more work is needed to fully understand the connection.

It also helps to know that not all hair loss is the same. The kind linked to weight loss, called telogen effluvium, differs from male or female pattern baldness, which is driven by genes and hormones over many years. It is also different from alopecia areata, an autoimmune condition where the body’s immune system mistakenly attacks the hair follicle. Interestingly, the new study did not find a clear link between GLP-1 drugs and alopecia areata, which suggests the immune system is probably not the key driver here. Knowing which type of hair loss you are dealing with matters, because the causes and the treatments are different.

What You Can Do About It

If you are on one of these medications and notice more hair on your brush or pillow, do not panic, and do not stop your medication without talking to your doctor first. For most people, the shedding is temporary. Hair typically starts growing back within three to six months once the body adjusts.

What are the researchers and physicians suggesting regarding handling this type of hair loss? A few steps may help. Losing weight more gradually, rather than quickly, may ease the shock to your system. Eating enough protein and a variety of nutrient-rich foods, including fruits, vegetables, and lean meats, supports healthy hair growth. Staying well hydrated matters too, since dehydration can make shedding worse.

If you are concerned, ask your doctor to check your iron, zinc, and vitamin levels, since correcting a true deficiency can make a real difference. Remember, you must consult your prescriber regarding any recommended changes to handle this situation and not do it without this guidance.

If the shedding is heavy, does not improve, or bothers you, see a board-certified dermatologist. They can rule out other causes, such as thyroid problems or an unrelated condition like alopecia areata, and recommend treatments. Some patients find that platelet-based scalp treatments or targeted supplements help once a true nutrient gap is identified, though the evidence behind many over-the-counter hair products is still thin, so it pays to ask a professional before spending money on them.

It is worth keeping this risk in perspective. These medications have real, well-documented benefits, including better blood sugar control, weight loss, and a lower risk of heart disease for many patients. The hair loss risk found in this study was real but small, and mostly reversible. Knowing about it ahead of time simply means you and your doctor can watch for it, and act early if it happens.