GLP-1 drugs are a class of medications that mimic a natural gut hormone called GLP-1 (glucagon-like peptide-1), which your body releases after eating. They were originally developed to treat type 2 diabetes but have become widely known for their effectiveness in weight loss. Most are given as weekly injections, though one oral option exists.
How GLP-1 Drugs Work
After you eat, your gut naturally releases GLP-1 to signal that food has arrived. GLP-1 drugs deliver a synthetic version of this hormone that’s far more potent and longer-lasting than what your body produces on its own. They work through three main pathways simultaneously.
First, they slow down how quickly your stomach empties food into your intestines. This keeps you feeling full longer after a meal, which naturally reduces how much you eat. Second, they act on the pancreas to boost insulin release in response to rising blood sugar, helping keep glucose levels in check. Third, and perhaps most importantly for weight loss, they act directly on appetite centers in the brain. They increase the activity of signals that suppress hunger while dialing down the signals that drive you to eat, including the reward response that makes food feel pleasurable.
Available GLP-1 Medications
Several GLP-1 drugs are on the market, and the differences between them come down to how often you take them, how they’re delivered, and what they’re approved to treat.
- Semaglutide (Ozempic): Weekly injection approved for type 2 diabetes
- Semaglutide (Wegovy): Weekly injection approved for chronic weight management
- Semaglutide (Rybelsus): Daily oral tablet approved for type 2 diabetes
- Liraglutide (Victoza): Daily injection approved for type 2 diabetes
- Liraglutide (Saxenda): Daily injection approved for weight management
- Dulaglutide (Trulicity): Weekly injection approved for type 2 diabetes
- Exenatide (Byetta): Twice-daily injection approved for type 2 diabetes
- Exenatide extended-release (Bydureon BCise): Weekly injection approved for type 2 diabetes
Semaglutide and liraglutide are the only GLP-1 drugs with separate FDA approvals specifically for weight management, though weight loss occurs with all of them. The same active ingredient, semaglutide, is sold under different brand names depending on the condition it’s prescribed for: Ozempic for diabetes, Wegovy for obesity.
Dual Agonists: The Newer Category
Tirzepatide (sold as Mounjaro for diabetes and Zepbound for weight loss) is often grouped with GLP-1 drugs, but it’s technically a dual agonist. It activates both the GLP-1 receptor and a second gut hormone receptor called GIP. This dual action appears to produce stronger results. GIP and GLP-1 both stimulate insulin release and act on satiety centers in the brain, but they have complementary effects on fat metabolism: GIP directly promotes fat storage in healthy fat cells while GLP-1 indirectly promotes fat breakdown. Together, they help reduce harmful fat buildup around organs.
In the head-to-head SURMOUNT-5 trial, tirzepatide produced 47% greater weight loss than semaglutide. Participants on tirzepatide lost an average of 20.2% of their body weight (about 50 pounds), compared to 13.7% (about 33 pounds) with semaglutide. Tirzepatide also edges ahead on blood sugar control, lowering A1C levels by 2% to 2.5% compared to about 1% to 2% with semaglutide.
What They’re Used For
The FDA approves GLP-1 drugs for two primary conditions: type 2 diabetes and chronic weight management in people with obesity or overweight with a weight-related health condition. They are not approved for type 1 diabetes.
Beyond blood sugar and weight, GLP-1 drugs have demonstrated meaningful cardiovascular benefits. A meta-analysis of eight large cardiovascular trials covering over 60,000 patients, published in the American Heart Association’s journal Circulation, found a 14% reduction in major adverse cardiovascular events, including heart attack, stroke, and cardiovascular death. Hospitalizations for heart failure dropped by 10% to 11%. These heart benefits are a significant reason doctors prescribe GLP-1 drugs even when blood sugar control alone might be achievable with older, cheaper medications.
Common Side Effects
Gastrointestinal problems are by far the most frequent side effects, which makes sense given that these drugs work partly by slowing digestion. Nausea is the most common complaint, followed by vomiting, diarrhea or constipation, abdominal discomfort, and acid reflux. Fatigue and dizziness (often related to dehydration from the GI symptoms) also occur. These side effects tend to be worst during the initial weeks of treatment and when the dose is increased, which is why doctors start at a low dose and gradually raise it over several months.
GLP-1 drugs should not be used during pregnancy, and people of childbearing potential are advised to use effective contraception while on treatment. Because these drugs can cause rapid weight loss, fertility may actually increase in people who were previously not ovulating regularly due to obesity, which makes contraception planning especially important.
Injection vs. Oral
Nearly all GLP-1 drugs are subcutaneous injections, meaning you inject them just under the skin of your abdomen, thigh, or upper arm using a prefilled pen. The needle is small and the process takes seconds. Most of the newer options are once-weekly injections, which has made them far more convenient than the twice-daily or daily injections required by older drugs like exenatide (Byetta) and liraglutide (Victoza).
The one oral option is Rybelsus, an oral semaglutide tablet taken daily. It needs to be taken on an empty stomach with no more than 4 ounces of plain water, and you have to wait at least 30 minutes before eating, drinking, or taking other medications. This makes it less convenient than it might sound, and the oral form generally produces slightly less weight loss than the injectable version.
Weight Regain After Stopping
One practical reality that catches many people off guard: weight tends to return after stopping GLP-1 drugs. These medications suppress appetite and slow digestion only while you’re taking them. Once you stop, the hormonal signals return to baseline, and hunger and eating patterns typically revert. This is why most prescribers consider GLP-1 therapy a long-term or indefinite treatment for weight management rather than a short-term fix. The same is true for blood sugar control in diabetes; stopping the medication generally means glucose levels rise again.