In recent years, medicines originally developed for diabetes management have gained attention for their role in weight loss and metabolic health. Among them, liraglutide, semaglutide, and tirzepatide are the most widely discussed. While they share similarities, each has distinct features in terms of how they work, their effectiveness, and their side effects.
This article explains their differences in a clear, respectful way for the general population.
What Are They?
- Liraglutide (Saxenda, Victoza) – daily injectable, first approved for diabetes, later for weight management.
- Semaglutide (Ozempic, Wegovy) – weekly injectable, widely known for strong weight reduction.
- Tirzepatide (Mounjaro, Zepbound) – the newest, with a dual mechanism, giving it greater potential in both diabetes and obesity care.
How Do They Work?
- Liraglutide & Semaglutide: mimic GLP-1, a natural gut hormone that increases insulin, slows stomach emptying, and reduces appetite.
- Tirzepatide: mimics both GLP-1 and GIP, providing a dual effect that enhances satiety and glucose control, making it especially powerful.
Who Are These Medications For?
These treatments are not meant for everyone. Doctors prescribe them under specific conditions, where the benefits outweigh the risks.
- For Diabetes:
- People with type 2 diabetes who need better blood sugar control.
- Particularly useful for those who also carry excess weight or have high cardiovascular risk.
- For Obesity and Weight Management:
- Adults with a BMI of 30 or higher (classified as obesity).
- Adults with a BMI of 27 or higher plus weight-related health conditions (such as high blood pressure, high cholesterol, or sleep apnea).
- Prime Candidates:
- Individuals who have tried diet, exercise, and lifestyle changes but still struggle to lose weight.
- People at risk of diabetes, heart disease, or fatty liver, where weight reduction could significantly improve health.
- Patients motivated to combine medication with long-term lifestyle adjustments, not seeking a “quick fix.”
- Not Suitable For:
- People with type 1 diabetes.
- Women who are pregnant or breastfeeding.
- Anyone with a personal or family history of certain thyroid cancers or multiple endocrine neoplasia type 2 (MEN2).
- Those with active pancreatitis or severe gastrointestinal disease.
Efficacy: How Well Do They Work?
Clinical studies have shown clear differences in their outcomes.
- Liraglutide:
- Average weight loss: about 5–8% of body weight over a year.
- Improves blood sugar levels and lowers cardiovascular risk in patients with diabetes.
- Semaglutide:
- Average weight loss: 10–15% of body weight, with some patients achieving more.
- More potent than liraglutide, partly due to its longer action (weekly injection instead of daily).
- Tirzepatide:
- Average weight loss: 15–20% of body weight, often approaching results similar to bariatric surgery.
- Particularly effective for people with both obesity and type 2 diabetes.
Side Effects: What to Expect
While generally safe, these medicines are not without side effects. Most are linked to their effect on the digestive system.
- Common side effects (for all three):
- Nausea, vomiting, diarrhea, constipation, bloating, or indigestion.
- These usually lessen over time as the body adjusts.
- Less common but more serious risks:
- Inflammation of the pancreas (pancreatitis).
- Gallbladder problems (such as gallstones).
- Rare concerns about thyroid tumors, based on animal studies.
- Practical differences:
- Liraglutide requires daily injections.
- Semaglutide and tirzepatide are given once weekly, making them easier to use.
Quick Comparison Table
| Feature | Liraglutide | Semaglutide | Tirzepatide |
| Brand names | Saxenda, Victoza | Ozempic, Wegovy | Mounjaro, Zepbound |
| How often? | Daily injection | Weekly injection | Weekly injection |
| Mechanism | GLP-1 agonist | GLP-1 agonist | Dual: GLP-1 + GIP |
| Weight loss | 5–8% | 10–15% | 15–20% |
| Diabetes effect | Improves sugar & CV risk | Strong glucose control | Strongest effect in diabetes |
| Side effects | GI upset, gallstones, rare pancreatitis | Similar to liraglutide | Similar, with possibly more nausea early on |
| Track record | Longest safety data | Moderate safety data | Newest, promising but still being studied |
What to Expect as a Patient
Starting one of these medications is not a “quick fix,” but a gradual process. Knowing what to expect—and how to manage the bumps along the way—can make the journey smoother.
- First Weeks:
Many people notice reduced appetite within the first few days. Mild nausea, bloating, or indigestion are also common.
What helps: eat smaller, slower meals; avoid rich, fatty, or spicy foods; stay well hydrated. - First 3 Months:
Weight reduction usually begins, though progress varies. Blood sugar control typically improves in those with diabetes. Some people may still experience nausea or diarrhea when doses are increased.
What helps: if symptoms are troublesome, discuss with your doctor—sometimes staying longer on a lower dose or adjusting the timing of injections eases discomfort. - 6–12 Months:
Weight loss is more noticeable and can reach 10–20% of body weight, depending on the medication. Energy, sleep, and confidence often improve. Digestive side effects usually settle by this stage.
What helps: continue supportive habits like balanced meals and physical activity, which also minimize constipation or reflux. - Long-Term:
For sustained benefits, most people remain on medication long-term. If treatment stops, weight regain is common. These medicines are most effective as part of a consistent health plan.
What helps: keep in touch with your healthcare provider for regular checks (weight, blood sugar, and monitoring for rare complications). - Important Caution:
Researchers are still studying the long-term safety of these medications. There have been concerns—though not yet proven in humans—about a possible link to pancreatic cancer or chronic pancreas problems. Rare cases of pancreatitis (inflammation of the pancreas) have been reported. Some patients may also develop elevated pancreatic enzymes without symptoms.
What helps: report severe abdominal pain, persistent nausea, or vomiting promptly. Doctors may check enzyme levels or recommend stopping the medication if problems arise.
Get in touch with Blooming Clinic to inquire about our services. (Bangkok Branch)
Frequently Asked Questions (FAQ)
1. Are these medications only for people with diabetes?
Not necessarily. Liraglutide, semaglutide, and tirzepatide are all approved for diabetes, but higher doses of liraglutide and semaglutide, and now tirzepatide, are also approved for obesity treatment in people without diabetes.
2. Do I still need diet and exercise if I take them?
Yes. These medicines work best when combined with healthy eating and regular physical activity. They are not replacements for lifestyle changes but rather powerful aids.
3. Do the side effects go away?
Most people find nausea and digestive discomfort improve after a few weeks. Doctors usually start with a low dose and gradually increase it to help the body adjust.
4. Can I stop the injections once I reach my goal weight?
Weight regain is common after stopping, because the appetite-regulating effect is lost. Many people may need to stay on treatment long-term, similar to how blood pressure or cholesterol medicines are continued.
5. Are they safe for everyone?
They are generally safe, but not recommended for people with certain conditions, such as a history of pancreatitis or rare thyroid cancers. A doctor’s evaluation is essential before starting.
Final Thoughts
Liraglutide, semaglutide, and tirzepatide have reshaped the treatment of diabetes and obesity. They offer powerful benefits, but each comes with its own considerations in terms of effectiveness, dosing, and side effects. The decision on which medication to use is best made with a healthcare professional, taking into account personal health goals and medical history.
References
- Pi-Sunyer X, et al. “A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management.” New England Journal of Medicine. 2015;373:11–22.
- Davies MJ, et al. “Semaglutide 2.4 mg once a week in adults with overweight or obesity.” New England Journal of Medicine. 2021;384:989–1002.
- Jastreboff AM, et al. “Tirzepatide Once Weekly for the Treatment of Obesity.” New England Journal of Medicine. 2022;387:205–216.
- Nauck MA, Meier JJ. “Incretin hormones: Their role in health and disease.” Diabetes, Obesity and Metabolism. 2018;20 Suppl 1:5–21.
- Wilding JPH, et al. “Once-Weekly Semaglutide in Adults with Overweight or Obesity.” New England Journal of Medicine. 2021;384:989–1002.
- American Diabetes Association. “Pharmacologic Approaches to Glycemic Treatment: Standards of Medical Care in Diabetes—2025.” Diabetes Care. 2025;48(Suppl. 1).
- Kushner RF, Kahan S. “Introduction: The state of obesity in 2022.” Medical Clinics of North America. 2022;106(1):xiii–xxi.
- Marso SP, et al. “Liraglutide and Cardiovascular Outcomes in Type 2 Diabetes.” New England Journal of Medicine. 2016;375:311–322.
- Sattar N, McGuire DK. “Pathways to Cardiovascular Benefit with GLP-1 Receptor Agonists: Beyond Glucose Lowering.” Diabetes, Obesity and Metabolism. 2021;23(1):3–12.
- Frias JP, et al. “Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes.” New England Journal of Medicine. 2021;385:503–515.