GLP-1 medications are a class of drugs that mimic a natural gut hormone to lower blood sugar, reduce appetite, and promote weight loss. Originally developed for type 2 diabetes, they’ve become some of the most prescribed medications in the world after proving remarkably effective for weight management as well. The most recognized brand names include Ozempic, Wegovy, Mounjaro, and Zepbound.
How GLP-1 Medications Work
Your small intestine naturally produces a hormone called GLP-1 (glucagon-like peptide-1) after you eat. This hormone does three important things: it signals your pancreas to release insulin, it blocks a second hormone called glucagon that would otherwise raise your blood sugar, and it slows down how quickly food leaves your stomach. All three effects work together to keep blood sugar from spiking after meals.
GLP-1 medications are synthetic versions of this hormone. They bind to the same receptors as natural GLP-1, triggering identical effects but lasting much longer in the body. The natural hormone breaks down within minutes. The medications are engineered to persist for days, which is why most are given as a once-weekly injection. The slower stomach emptying is also a big reason people feel full sooner and eat less on these drugs.
Available Medications
The major GLP-1 medications currently on the market include semaglutide (sold as Ozempic and Wegovy), liraglutide, and dulaglutide. Ozempic is approved for type 2 diabetes, while Wegovy is the same drug at a higher dose approved specifically for weight management. Most are given as a weekly injection using a prefilled pen, though semaglutide also comes in a daily oral tablet. The oral version has specific requirements: you swallow it on an empty stomach with no more than half a glass of water, then wait at least 30 minutes before eating, drinking, or taking other medications.
Tirzepatide (sold as Mounjaro for diabetes and Zepbound for weight loss) represents a newer approach. Rather than targeting only the GLP-1 receptor, it activates two receptors simultaneously, adding GIP (another gut hormone involved in metabolism) to the mix. This dual action appears to produce stronger results. In a head-to-head trial, tirzepatide delivered 47% greater weight loss than semaglutide, with patients losing an average of 20.2% of their body weight compared to 13.7% on semaglutide.
Weight Loss Results
The weight loss from these medications is substantial compared to older options. In the STEP 1 trial, people taking semaglutide (Wegovy) lost an average of about 35 pounds, or roughly 15% of their body weight, over about 68 weeks. Those on placebo lost around 6 pounds. A newer higher-dose version of Wegovy pushed average weight loss to about 21% of body weight.
Tirzepatide produced even larger results. In the SURMOUNT-1 trial of adults without diabetes, those on the highest dose lost an average of 48 pounds, roughly 21% of their body weight, over 72 weeks. Even the lowest dose led to about 34 pounds of weight loss. People with type 2 diabetes typically lose somewhat less, around 13 to 15% of body weight, likely because diabetes itself makes weight loss harder.
Blood Sugar and Heart Benefits
For people with type 2 diabetes, these medications lower A1C (a measure of average blood sugar over three months) by about 1.5 to 1.6 percentage points. That’s a clinically meaningful drop, often enough to bring someone from poorly controlled diabetes into a well-managed range.
Beyond blood sugar, GLP-1 medications also reduce the risk of heart attacks, strokes, and cardiovascular death. Across eight large cardiovascular outcome trials, GLP-1 drugs reduced the combined rate of these major cardiac events by about 14 to 15%. This benefit appears to go beyond what you’d expect from improved blood sugar alone, suggesting the drugs have direct protective effects on the cardiovascular system.
Common Side Effects
Gastrointestinal problems are by far the most frequent side effects, which makes sense given that these drugs slow digestion. A 2025 RAND Corporation survey of U.S. adults who have taken a GLP-1 medication found that 52% experienced nausea, 34% had diarrhea, and about 20% experienced vomiting. The good news is that most of these side effects are mild. Serious nausea was reported by fewer than 9% of users, and serious vomiting by about 5%.
These side effects tend to be worst when starting the medication or moving up to a higher dose, which is why doctors typically start at the lowest dose and increase gradually over several weeks or months. For many people, the nausea fades significantly after the first few weeks as the body adjusts.
Important Safety Warnings
All semaglutide and tirzepatide products carry an FDA boxed warning about thyroid tumors. In animal studies, these drugs caused a type of thyroid cancer called medullary thyroid carcinoma. Whether this risk applies to humans isn’t fully established, but the medications are contraindicated for anyone with a personal or family history of medullary thyroid carcinoma or a rare genetic condition called Multiple Endocrine Neoplasia syndrome type 2. If you have either of these in your medical history, these drugs are not an option.
What Taking GLP-1 Medication Looks Like
For most people, the experience starts with a low dose injected once a week using a small prefilled pen, similar to what people use for insulin. The needle is thin and short, and injections go into the stomach, thigh, or upper arm. The dose increases every four weeks or so until reaching the target. Reaching the full therapeutic dose typically takes two to four months depending on the specific medication.
One practical consideration is that these medications need to be refrigerated before first use. Cost and access have also been significant barriers. Brand-name GLP-1 medications carry high list prices, and insurance coverage varies widely depending on your plan and whether the prescription is for diabetes or weight loss. Demand has been high enough to cause supply shortages for some products in recent years, though availability has been improving.
Weight loss and blood sugar improvements typically plateau after about a year to 18 months on the medication. Most clinical evidence suggests that stopping the drug leads to gradual weight regain, which is why many people stay on these medications long-term.