Potential Side Effects of Weight Loss Drugs. How to deal with any effects

June 6, 2025

Learn what to do if you suffer side effects of weight loss drugs.

Weight loss drugs—whether prescription medications like semaglutide (Ozempic, Wegovy), liraglutide (Saxenda), phentermine, orlistat, or others—can be effective, but they come with potential side effects.

Here’s a breakdown of the common and serious ones:

Common Side Effects (vary by drug class)

GLP-1 Receptor Agonists (e.g., Ozempic, Wegovy, Saxenda)

• Nausea
• Vomiting
• Diarrhoea or constipation
• Stomach pain
• Loss of appetite
• Fatigue
• Headache

Stimulant-Based Suppressants (e.g., phentermine)

• Increased heart rate
• High blood pressure
• Insomnia
• Dry mouth
• Anxiety or restlessness
• Dizziness

Fat Absorption Inhibitors (e.g., orlistat)

• Oily stools
• Frequent bowel movements
• Gas with discharge
• Abdominal cramping
• Fat-soluble vitamin deficiency (A, D, E, K)

Serious Side Effects (rare, but important)

• Pancreatitis (GLP-1 drugs)
• Gallstones or gallbladder disease
• Kidney injury
• Thyroid tumors (seen in animal studies with GLP-1s)
• Heart valve issues (older drugs like fen-phen, now off the market)
• Depression or suicidal thoughts (especially with medications like bupropion/naltrexone combos)

Risks Increase When:

• Taken without medical supervision
• Combined with other drugs unsafely
• Used for cosmetic purposes rather than medical need

Dealing with side effects

Countering the side effects of weight loss drugs depends on the specific medication and which side effects you’re dealing with. Here’s a targeted breakdown of strategies and supportive measures:

For GLP-1 Drugs (Ozempic, Wegovy, Saxenda)

Side Effects: Nausea, vomiting, diarrhoea, constipation, appetite loss, fatigue

What Can Help:

• Eat smaller meals and avoid fatty or fried foods
• Ginger tea or ginger supplements for nausea
• Hydration + electrolyte drinks for diarrhea
• Fiber supplements (e.g., psyllium husk) for constipation
• Gradual dose titration (often prescribed this way to reduce GI issues)
• Prescription anti-nausea meds (like ondansetron if needed)

For Stimulants (Phentermine, Qsymia)

Side Effects: High blood pressure, insomnia, anxiety, dry mouth

What Can Help:

• Avoid caffeine and stimulants
• Take the medication early in the day to reduce insomnia
• Melatonin or sleep hygiene practices to help sleep
• Hydrate frequently + sugar-free gum for dry mouth
• Monitor blood pressure regularly; report sustained elevation to your doctor
• CBT or mindfulness techniques for anxiety symptoms

For Orlistat (Alli, Xenical)

Side Effects: Oily stools, gas, urgent bowel movements, vitamin deficiencies

What Can Help:

• Stick to a low-fat diet (reduces GI side effects significantly)
• Take a multivitamin at bedtime (or at least 2 hours away from orlistat)
• Use anti-gas meds like simethicone if needed
• Activated charcoal or digestive enzymes (anecdotal, limited evidence)

To Reduce Risk of Serious Side Effects

• Routine blood tests (kidney, liver function, electrolytes)
• Ultrasound or thyroid screening if risks are high
• Stop drug immediately if you experience severe abdominal pain, signs of pancreatitis, or mood changes
• Use only under medical supervision – especially for people with heart conditions, psychiatric issues, or endocrine disorders

Much has been written about weight loss drugs and there are alternatives – read our post Ozempic Natural Alternatives. If you are interested though and we have a report on the potential benefits, you should certainly consult your doctor.