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Wegovy® vs. Qysmia® - Everything You Should Know

Written on September 26, 2023 by Lori Mulligan, MPH. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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Contemplating a weight loss medication? Want to know the differences between Wegovy®(semaglutide) vs. Qysmia®(phentermine-topiramate)? Let’s take a closer look at Wegovy® vs. Qysmia®.

What Is Wegovy®and How Does It Work?

Wegovy®is the brand name for the high-dose injectable peptide hormone molecule known as semaglutide, a medication that was previously approved by the FDA under the brand names Rybelsus®(oral) and Ozempic®(lower-dose injection) for the treatment of type 2 diabetes. Injectable semaglutide eliminates the strict guidelines for ingesting on an empty stomach required by oral semaglutide. The higher-dose Wegovy®also allows for better crossing of the blood-brain barrier, increasing its weight-loss efficacy.

Semaglutide is in a class of medications known as glucagon-like peptide-1 receptor agonists, or GLP-1 RAs. GLP-1 is a hormone naturally released in the gastrointestinal tract in response to nutrient intake. It has multiple effects, including increasing insulin release from the pancreas, slowing down stomach emptying, and targeting receptors in the brain that cause appetite reduction. This results in a sensation of satiety, or fullness, lasting much longer than possible with natural GLP-1 hormone levels.

What Are the Risks and Benefits of Wegovy®?

Phase 3 clinical trials of Wegovy®, dubbed the STEP (Semaglutide Treatment Effect in People with Obesity) trials, were conducted in a variety of clinical scenarios, each varying slightly in the study population and design. The widely reported STEP 1 trial, the results of which were published in the New England Journal of Medicine, demonstrated an average of 14.9% body weight reduction after 68 weeks of therapy in those assigned to the medication group, versus only 2.4% weight loss in those assigned to the placebo group. The average weight loss seen with existing anti-obesity medications is typically about 5% to 9%, while those engaged in lifestyle and behavioral therapy alone are expected to lose only 3% to 5% of their body weight.[1]

The most common side effects of Wegovy® in adults or children aged 12 years and older may include:

  • Nausea
  • Stomach (abdomen) pain
  • Dizziness
  • Stomach flu
  • Diarrhea
  • Headache
  • Feeling bloated
  • Heartburn
  • Vomiting
  • Tiredness
  • Belching
  • Runny nose or sore throat
  • Constipation
  • Upset stomach
  • Gas

Serious potential side effects include [2]:

  • Pancreatitis
  • Gallbladder problems
  • Hypoglycemia in patients with type 2 diabetes
  • Kidney problems
  • Serious allergic reactions
  • Change of vision in people with type 2 diabetes
  • Increased heart rate
  • Depression or thoughts of suicide


Phentermine and topiramate combination is used together with a reduced-calorie diet and proper exercise to help you lose and maintain weight. It is also used in overweight people who may also have diabetes, high blood pressure, high cholesterol, or heart disease.

Everlywell Weight Loss Support

Is Qysmia® Habit-Forming?

Take this medicine only as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. If too much is taken, it may become habit-forming.[3]

What Should I Watch for While Using This Medication?

Visit your healthcare provider for checks on your progress.

Do not stop taking it except on your healthcare provider's advice. You may develop a severe reaction.

Do not take this medicine close to bedtime. It may prevent you from sleeping.

Avoid extreme heat. This medicine can cause you to sweat less than normal. Your body temperature could increase to dangerous levels, which may lead to heat stroke.

You should drink plenty of fluids while taking this medicine. If you have had kidney stones, this will help to reduce your chances of forming kidney stones.

You may get drowsy or dizzy. Do not drive, use machinery, or do anything that needs mental alertness until you know how this medicine affects you. Do not stand or sit up quickly, especially if you are older. Avoid alcoholic drinks.

This medicine may affect blood sugar levels. Ask your healthcare provider if changes in diet or medicines are needed if you have diabetes.

Check with your healthcare professional if you have severe diarrhea, nausea, and vomiting.

Patients and their families should watch out for new or worsening depression or thoughts of suicide. Also watch out for sudden changes in feelings such as feeling anxious, agitated, panicky, irritable, hostile, aggressive, impulsive, severely restless, overly excited, and hyperactive. If this happens, call your healthcare provider.

Birth control may not work properly while you are taking this medicine. Talk to your healthcare provider about using an extra method of birth control.

Women should inform their healthcare provider if they wish to become pregnant or think they might be pregnant. There is a potential for serious side effects and harm to an unborn child. Losing weight while pregnant is not advised and may cause harm to the unborn child.[4]

What Side Effects May I Notice From Receiving This Medication?

Side effects of Qsymia® include headache, upper respiratory symptoms, acute loss of vision, eye pain, constipation, insomnia, dizziness, paresthesia, palpitations, back pain, nausea, and diarrhea.

Renal effects consist of increased serum creatinine in patients, which occurs primarily four to eight weeks into treatment.

Topiramate has been associated with glaucoma and hyperthermia.

Hyperchloremic metabolic acidosis can occur due to decreased serum bicarbonate concentrations from increased renal bicarbonate loss. Patients on Qsymia® who are also taking antihypertensive medications may experience hypotension; therefore, close monitoring of blood pressure and adjustment of medication is recommended in these cases.

Patients who start on Qsymia® and begin to experience untoward side effects should be slowly weaned off the medication over 7 days to minimize the risk of seizure.[5]

Everlywell Offers Online Weight Loss Program and Metabolism Test

Everlywell’s Weight Care+ program pairs GLP-1 prescriptions with regular clinician care, lab testing, and support for related conditions.

You can also test hormones that may be related to unexpected changes in weight and energy with Everlywell’s metabolism kit.

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  1. Anekwe C. A new treatment for obesity. Harvard Health Publishing. 9/10/21. Accessed on 9/12/2023.
  2. Medication guide: Wegovy®. FDA. Accessed on 9/17/2023.
  3. Phentermine and topiramate (Oral route). Mayo Clinic. 9/1/2023. Accessed on 9/16/2023.
  4. Phentermine; topiramate extended-release capsules. Cleveland Clinic. Accessed on 9/16/2023.
  5. Side effects of new weight loss medications. The Journal of Urgent Care Medicine. 3/1/2014. Accessed on 9/17/2023.
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