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A highly effective class of weight loss drug has taken the world by storm, as medications like Ozempic, Wegovy, and Zepbound become household names. These drugs, originally meant to treat diabetes, have become widely known for their slimming side effects.
Surging demand for these drugs has transformed pharmaceutical giants Novo Nordisk and Eli Lilly into some of the world’s most valuable companies — potentially paving the way for the first $1 trillion pharma firms. Morgan Stanley (MS) analysts anticipate the global market for highly-coveted treatments will reach $105 billion by 2030.
This guide will break down everything you need to know about these drugs, their differences, how they work, and their potential side effects.
What are weight loss drugs?
Ozempic, Wegovy, and Zepbound are all considered incretin medications, drugs that influence a group of hormones that impact insulin production in the body. These treatments work by spiking certain gut hormones that regulate blood sugar levels. Incretin drugs were originally only meant to be used for treating diabetes, but because they have also been found to reduce a user’s appetite, they have now been officially approved for weight loss and other health benefits.
What is Ozempic?
Ozempic is a blockbuster diabetes drug produced by the Danish pharma giant Novo Nordisk. It is part of a class of drugs known as glucagon-like peptide-1 receptor agonists (GLP-1 RAs).
This class of drugs was first developed in the 1990s when scientists identified a hormone-like molecule in the venom of a Gila monster, a lizard native to the American Southwest, that stimulated insulin secretion.
Fast-forward a decade later, and companies like Novo Nordisk (NVO) and Eli Lilly (LLY) started selling synthetic versions of this molecule to treat diabetes.
In December of 2017, the U.S Food and Drug Administration (FDA) approved Novo Nordisk’s semaglutide (brand name Ozempic) for the treatment of type-2 diabetes.
Ozempic is one of the most advanced versions of these drugs currently on the market, as previous versions required at least once-daily injections. Ozempic is administered just once a week.
Because the drug regulates blood sugar levels, reduces appetite, and slows down stomach emptying, one of its side effects is weight loss.
What is the difference between Ozempic and Wegovy?
After Ozempic’s slimming side effects became widely known, doctors started prescribing it off-label to treat a condition outside the drug’s official approval: weight loss.
Novo Nordisk also tested semaglutide, the active ingredient behind Ozempic, in higher doses as a weight loss drug.
In 2021, the FDA approved these higher doses of semaglutide, under the brand name Wegovy, for weight loss.
As a result, in the United States and some other countries, semaglutide is prescribed and sold as Ozempic when prescribed for diabetes and as Wegovy for weight loss.
Are there alternatives? Zepbound vs. Wegovy
Novo Nordisk is one of two pharma companies that are currently selling branded GLP-1 treatments. U.S.-based Eli Lilly is the other one.
Eli Lilly’s most advanced GLP-1 drugs are Mounjaro for diabetes and Zepbound for weight loss. The active ingredient behind both these drugs is tirzepatide.
The main difference between semaglutide and tirzepatide is that the latter mimics two gut hormones — not just one — GLP-1 and glucose-dependent insulinotropic polypeptide (GIP).
How do GLP-1 drugs help with weight loss?
GLP-1 and GIP are chemicals that are known as incretin hormones. These hormones are secreted by the intestines after a person eats to regulate blood sugar levels.
Drugs like semaglutide and tirzepatide increase the presence of GLP-1 and/or GIP in the human body to unnaturally high levels.
Scientists aren’t sure how or why but at these spiked-up levels the hormones reduce a person’s appetite.
In short, the primary reason GLP-1 drugs lead to weight loss is that people taking them eat less than they normally do.
How fast do GLP-1 drugs work for weight loss?
Different GLP-1 treatments have been found to work at varying speeds, according to clinical trials.
The highest dose of Novo Nordisk’s Wegovy led to an average 15% of weight loss after 68 weeks in clinical trials.
Patients taking the highest dose of Eli Lilly’s Zepbound lost over 20% of their weight after 72 weeks.
To summarize, GLP-1 drug users can expect to lose an average of 15% to 20% of their weight over the course of a year and four months.
How do you take GLP-1 drugs?
GLP-1 treatments are typically administered as weekly injections.
Wegovy and Zepbound are both taken once-weekly via a subcutaneous injection, or under the skin. A month’s supply of both drugs comes with four single-dose, auto-injector pens — similar to EpiPens.
Off-brand versions of these treatments are often sold in single or multi-dose vials.
Additionally, Novo Nordisk sells a pill form of semaglutide, under the brand name Rybelsus, for treating type 2 diabetes.
How much do GLP-1 drugs cost?
The retail price, without insurance, of Wegovy is $1,349.02 for a month’s supply. Zepbound’s list price for most of its doses is $1,059.87 a month. However, it’s important to note that these list prices don’t reflect what most customers pay after insurance and available manufacturer rebates are applied.
Additionally, Eli Lilly started offering single-dose vials — instead of auto-injector pens — of its two lowest doses of Zepbound for $399 and $549 a month, respectively. This option must be paid out-of-pocket.
A growing number of companies are now offering generic versions of these treatments, often priced hundreds of dollars lower than their branded counterparts.
Does insurance cover GLP-1 drugs?
Insurance coverage for GLP-1 drugs for the use of weight loss varies by plan. Some insurance companies and employers have refused to cover the medication due to their high cost.
A Morgan Stanley survey conducted earlier this year among GLP-1 drug users — including those using the treatments for diabetes — found that about two-thirds of respondents had their medication fully covered by insurance. Those paying out-of-pocket reported an average monthly cost of $196.
Novo Nordisk claims that the majority of patients with insurance coverage pay $25 or less for a month’s supply of Ozempic or Wegovy.
Additionally, Medicare started covering Wegovy this year for patients who are prescribed the medication as a way to reduce their risk of serious heart events such as heart attacks and strokes.
What are the side effects?
Wegovy and Zepbound have the same side effects.
Both Novo Nordisk and Eli Lilly caution that their weight loss drugs may cause serious side effects, including the potential risk of thyroid tumors. They advise that patients with a family history of medullary thyroid carcinoma, a type of thyroid cancer, or those with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), should not use these medications.
Other serious side effects include:
- Pancreatitis (severe abdominal pain)
- Gallbladder problems (pain, jaundice)
- Low blood sugar, especially if using other diabetes medications
- Kidney issues from dehydration
- Serious allergic reactions (swelling, breathing issues)
- Changes in vision for people with type 2 diabetes
- Increased heart rate
- Depression or suicidal thoughts
However, the most common side effects are nausea, diarrhea, vomiting, constipation, stomach pain, headache, and fatigue.
What is Ozempic face?
Ozempic face is a non-medical term coined by cosmetic and celebrity dermatologist Dr. Paul Jarrod Frank, who observed the phenomenon among patients using weight-loss drugs. As these medications gained popularity, more patients began expressing concerns about changes in their facial appearance.
Sudden weight loss can rapidly reduce facial fat, leading to changes such as skin shrinkage, sagging, and decreased elasticity. As the skin loses elastin and collagen, it becomes harder for it to retract after significant fat loss, resulting in pronounced signs of aging, loose or sagging skin, and a hollowed appearance.
Are GLP-1s linked to suicidal thoughts?
Probes from several health regulators, including the U.S Food and Drug Administration (FDA), the U.K.’s Medicines and Healthcare products Regulatory Agency (MHRA), and the European Medicines Agency, have all failed to find evidence that link GLP-1 drugs to suicide, suicidal thoughts, or actions.
These investigations followed reports of individuals taking semaglutide and similar drugs exhibiting such behavior.
While the FDA couldn’t rule out a “small risk,” it noted that a study funded by the NIH found patients on semaglutide had a lower risk of suicidal thoughts compared to those on other diabetes and anti-obesity medications.
Georgios Schoretsanitis, lead author of a separate study, acknowledged no clear evidence of a causal relationship between semaglutide and suicidal ideation, but noted a potential association. His research, based on WHO data, found a 45% higher risk of reported suicidal thoughts in patients taking semaglutide. He cautioned that the results show an association, not proof of causation, and highlighted an increased risk in patients also on antidepressants. He advises clinicians to assess patients’ mental health before starting treatment.
Do GLP-1 drugs have other health benefits?
Novo Nordisk and Eli Lilly have been testing their medications for uses outside of weight loss and diabetes.
For example, earlier this year the FDA approved the use of Wegovy for reducing the risk of heart attacks, strokes, and other cardiovascular events for people who are overweight or obese. The change came just months after Novo Nordisk announced results from a clinical trial that found the drug cut the risk of serious heart events by 20%.
For its part, Eli Lilly announced this year that tirzepatide was found to help alleviate sleep apnea in patients with obesity in late-stage clinical trials.
Both companies are also testing their medications for the treatment of heart failure.
Some studies have also found links between GLP-1s and a reduced risk of cancer, and alcohol and substance abuse.
Is there a shortage of GLP-1 drugs?
Both Eli Lilly and Novo Nordisk have been struggling to produce enough GLP-1 drugs to meet rising demand.
The FDA first declared a shortage of Wegovy in March of 2022. And the pharma company has been limiting starter doses of Wegovy since 2023 to ensure there’s enough supply for patients already on the drug. Novo Nordisk CEO Lars Fruergaard Jørgensen said this March that the gap between demand for weight loss drugs and the supply is significant enough to take years to close.
Mounjaro was first added to the FDA’s drug shortage list in 2022, while Zepbound was officially declared in limited supply this April.
All four drugs — Ozempic, Wegovy, Mounjaro and Zepbound — still remain on the health regulator’s drug shortage, despite all but one dose of Wegovy being listed as currently available on the site.
The FDA says that even when all doses of a drug are found to be available, there are other requirements that need to be fulfilled for a drug to be removed from the list, including whether backorders are being fulfilled.
Both Novo Nordisk and Eli Lilly are investing billions of dollars to ramp up production of these drugs.
Novo Nordisk announced in February that it has acquired three facilities from the company’s largest shareholder, Novo Holdings, for $11 billion in an effort to address a shortage of Wegovy. The deal was made in connection with Novo Holdings’ acquisition of the drug manufacturing company Catalent (CTLT). Novo Nordisk said in a statement that the acquisition will increase the company’s production capacity beginning in 2026.
Eli Lilly said in May that it will pile $5.3 billion into manufacturing its popular weight loss drugs, more than doubling its investment in a manufacturing facility in Lebanon, Indiana. The new spend brings the company’s total investment in the site to a whopping $9 billion, up from its original $3.7 billion commitment — making it now the largest manufacturing investment in the company’s history.
What are compounded GLP-1 drugs?
Compounding refers to the customization of an approved drug by a pharmacy or physician to meet the specific needs of an individual patient.
Typically, the Food, Drug, and Cosmetic Act prohibits compounding drugs that are just copies of commercially available medications. But drugs that are in shortage are not considered by the FDA to be commercially available. The limited supply of highly coveted and expensive brand name drugs like Wegovy has spurred several digital healthcare companies to take advantage of that provision.
Companies like Hims & Hers, Sesame, and Noom all started selling compounded versions of GLP-1 drugs for hundreds of dollars cheaper than branded versions.
However, there are risks. The compounded formulations are not FDA-approved, so the agency does not review the safety and efficacy of these products. Additionally, the FDA said in July that it had received reports of overdoses related to weight loss drugs, often due to confusion over proper dosing.
Which celebrities have taken GLP-1 drugs to lose weight? Oprah, Elon Musk, and more.
Dozens of celebrities have come out and shared their experience with weight loss drugs.
Late last year, Oprah Winfrey said she used prescription weight loss medications as a “maintenance tool.” Soon after the revelation, she left her seat from the board of WeightWatchers (WW). She had been a member of the board since 2015.
In 2022, Elon Musk posted on X, the social media platform he owns, that he had used Wegovy. Since then, Musk has become a big proponent of GLP-1 medications.
Other celebrities who have said they used these drugs are: Kelly Clarkson, Amy Schumer, Whoopi Goldberg, Tracy Morgan, and Chelsea Handler.
What is the future of weight loss drugs?
Several pharmaceutical companies are racing to introduce their own weight loss drugs to the market and disrupt the current duopoly held by Novo Nordisk and Eli Lilly.
These companies include Viking Therapeutics, which is developing both a weight loss injection and a pill. Larger pharma companies like Roche, Amgen (AMGN), and Pfizer are also working on their own anti-obesity drugs.
To combat the growing competition, Novo Nordisk and Eli Lilly are testing their drugs — as noted above — for other health benefits.
They’re also testing newer and more powerful meds.
Eli Lilly has nine obesity and diabetes drugs in development which could add even more health benefits to its portfolio of medications. These experimental treatments include a weight loss pill, orforglipron. The pill is currently in a phase 3 trial — its results will readout next year. Earlier trials found that it helped users lose an average of nearly 15% of weight after 36 weeks.
Eli Lilly is also testing a strong GLP-1 injection, retatrutide, which in a clinical trial helped patients lose 17% of their weight in 24 weeks.
Novo Nordisk is testing a weight loss pill of its own, amycretin. Novo Nordisk said that in a trial, patients that took a once-daily 50mg dose of amycretin lost an average of 10.4% of their weight in just three months. Trial participants that took two pills lost even more weight, 13.1% at three months.
The Danish pharma company is also developing a more potent obesity treatment called CagriSema. This new drug combines semaglutide with amylin and calcitonin receptor agonists. Amylin helps regulate blood sugar levels, similar to GLP-1, while calcitonin controls calcium levels in the blood. Results for two late-stage trials of the drug are expected this year.
