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Side Effects of Weight Loss Medicines

Side effects of prescription weight loss medication
Written by:

Rabia Khaliq

MSc in Applied Psychology

Dr. Bradley Noon



The medications listed on this website are provided for informational purposes only. Their inclusion does not guarantee that they will be prescribed to any individual, as treatment decisions are ultimately at the discretion of healthcare providers. This list is not exhaustive, and healthcare providers may prescribe other medications, including non-stimulant options, based on the patient’s unique health circumstances and needs.

Today, the market is flooded with various weight loss solutions, including dietary supplements and FDA-approved medications. However, despite their proven effectiveness for many patients, weight loss medicines may cause adverse reactions, and it’s important to be aware of these potential effects.

This article delves into the broader landscape of prescription medications used to treat overweight. The information below discloses their efficacy, possible side effects, and key considerations in choosing the right weight loss strategy.

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Are Weight Loss Medicines Dangerous?

The list of tainted [1*] weight loss solutions has increased in recent years in the US. These products have been found to contain laxatives, stimulants, antidepressants, diuretics, and even medications that are used to treat seizures. This category of products includes prescription medications and over-the-counter medications, and they are banned from sale in the US.

One example of medicines added to the above-mentioned list is sibutramine. It is a prescription weight loss medication that acts as both an appetite suppressant and a stimulant. It was previously available for legal purchase in the United States. However, further studies [2*] revealed that the risks associated with using sibutramine outweighed its benefits. People who used this medication had a higher risk of developing high blood pressure, an increased heart rate, and a heart attack or stroke, but they did not experience significant weight loss. As a result, the drug was removed [3*] from the market.

Furthermore, some diet pills may contain DNP, which is both illegal and extremely harmful. While such medications may contribute to quick weight loss, they offer an unhealthy method of boosting metabolism and might have major negative effects on the body. They also don’t promise to improve fitness or maintain weight loss in the long run.

Even legally approved medicines for losing weight may cause specific side effects. Just like the effectiveness of these medications, the occurrence of adverse reactions varies from one patient to another.

However, many weight loss medications do not contain dangerous ingredients and are FDA-approved for weight management. After a detailed assessment of your health history and weight loss goals, your healthcare provider will be able to determine the most suitable medication. It’s important to follow their recommendations and instructions and keep in touch during the whole course of treatment to address side effects promptly if they occur.

Make a smart choice by consulting qualified medical practitioners for your weight loss strategy.

Serious Side Effects of Weight Loss Medications

Weight loss medications have different mechanisms of action and different side effects. Some of them are mild while others are serious. Common negative side effects are the following:

  • Cardiovascular issues: Using certain diet pills may increase the risk of cardiovascular problems.
  • Issues with the circulatory system: If a person already has a cardiovascular disease, taking certain weight loss medications may increase their risk of stroke.
  • Problems with liver function: There have been instances [4*] where medicines used for weight loss have been connected to liver problems. Regular liver function monitoring is frequently advised.
  • Skin reactions: Some weight loss medicines may cause skin reactions, such as redness and itching.
  • Vision problems: When using certain weight reduction medications, some people may have changes in their eyesight or other visual abnormalities.
  • Neurological symptoms: Some weight reduction medications may cause dizziness or lightheadedness. Additionally, some people may hear ringing noises in their ears.

Each person may experience these side effects differently in terms of intensity and likelihood. Furthermore, research on the safety profile of weight loss medications continues, and new information may become available in the future.

Side Effects of the Most Popular Weight Loss Medications

Medication Name Common Side Effects Serious Side Effects
Phentermine (Adipex-P)
  • Insomnia
  • Dry mouth
  • Constipation
  • Increased heart rate
  • Elevated blood pressure
  • Primary pulmonary hypertension
  • Valvular heart disease
  • Dependence with prolonged use
Semaglutide (Wegovy and Ozempic)
  • Nausea
  • Diarrhea
  • Abdominal pain
  • Decreased appetite
  • Risk of thyroid tumors and pancreatitis.
Liraglutide (Saxenda)
  • Nausea
  • Vomiting
  • Diarrhea
  • Constipation
  • Risk of thyroid C-cell tumors
  • Pancreatitis
  • Gallbladder disease
Naltrexone-bupropion (Contrave)
  • Nausea
  • Constipation
  • Headache
  • Vomiting
  • Dizziness
  • Insomnia
  • Dry mouth
  • Seizures
  • Suicidal thoughts or actions
  • Increased blood pressure and heart rate
  • Liver damage
  • Allergic reactions
Orlistat (Xenical)
  • Gastrointestinal issues such as oily stools
  • Flatulence
  • Increased bowel movements
  • Rare instances of severe liver injury
Tirzepatide (Mounjaro)
  • Nausea
  • Vomiting
  • Diarrhea
  • Injection site reactions
  • Risk of thyroid tumor
  • Potential for hypoglycemia, especially when used in conjunction with other diabetes medications
Phendimetrazine (Bontril PDM)
  • Increased heart rate
  • Insomnia
  • Restlessness
  • Dry mouth
  • Constipation
  • Nervousness
  • Cardiovascular effects
  • Exacerbate anxiety
  • Agitation, or mood swings
  • Allergic reactions
  • Dependency and withdrawal symptoms

Can Diet Medications Be Safe?

When taken as directed under the guidance of a healthcare provider, diet pills are considered safe and can be beneficial. To make an informed decision regarding weight loss drug safety, it is important to consult with a medical practitioner and consider the following factors:

  • FDA approval: Medications approved by the FDA have gone through extensive testing determining their safety and effectiveness. Selecting medicines that have been approved and recommended by medical experts is essential.
  • Individual health status: Depending on a person’s medical history, current medical conditions, and other medications they may be taking, the safety of weight loss pills can vary. It is imperative that medical professionals perform a comprehensive evaluation prior to recommending any medication for weight loss.
  • Monitoring and follow-up: When taking diet pills, regular monitoring and follow-up with a medical practitioner is essential. This makes it possible to identify any possible adverse effects or difficulties early on and to modify the treatment strategy as necessary.
  • Combination therapies: A comprehensive weight-management approach encompasses exercise, dietary adjustments, and behavioral modifications, and may involve the prescription of weight-loss medication.
  • Patient education: Your healthcare provider should inform you about any potential adverse effects, share instructions on using the prescribed medication properly, and tell you about any essential precautions. Patients need to be aware of symptoms and indicators that can call for emergency care.

The Consequences of Abusing Weight Loss Supplements and Medications

Misusing weight loss medications and diet supplements might have detrimental effects on one’s health. The following are some possible repercussions of misusing prescription weight management medications and supplements:

  • Increased heart rate and blood pressure
  • Gastrointestinal distress
  • Hepatotoxicity
  • Dependence and addiction:
  • Hormonal imbalances
  • Renal dysfunction
  • Malnutrition
  • Nervousness and anxiety
  • Psychiatric effects like mood disorders

Signs of Addiction to Medications for Weight Management

It’s essential to identify the warning signs of addiction in order to seek the right support as soon as possible. The dependence on diet pills, particularly those that impact the central nervous system, can have detrimental effects on one’s health. Some symptoms include:

  • Obsessive thoughts related to weight loss: Persistent obsession with weight, body image, and the need to shed additional pounds despite having reached weight loss goals.
  • Compulsive usage: Using diet pills obsessively, taking them more often or in larger amounts than a doctor has recommended.
  • Loss of control: The inability to refrain from using diet pills in spite of the detrimental effects they may have on one’s relationships, daily life, physical or mental health, or both.
  • Obsession with getting pills: Devoting a substantial amount of time and effort to getting diet medications.
  • Physical symptoms: Misuse of weight loss medicines may cause physical symptoms including trembling, sleeplessness, elevated heart rate, excessive perspiration, or gastrointestinal problems.
  • Tolerance: Building up a resistance to the effects of diet pills, which makes higher dosages necessary to get the intended outcomes.
  • Withdrawal: Experiencing signs of withdrawal when trying to cut back or quit using diet medications. The symptoms of withdrawal can include extreme cravings, exhaustion, melancholy, and anger.
  • Deception: Using diet pills in a hidden manner, such as hiding pill bottles or lying to others about how much you use them.

Bottom Line

Before starting the use of prescription weight loss drugs, it is important to understand that the occurrence of adverse effects may depend on general health, pre-existing medical issues, and other medications being used. Additionally, individual responses to medications can vary greatly. Therefore, it is highly recommended to discuss the possible dangers and benefits with a healthcare professional. Regular monitoring and follow-ups are also essential over time to ensure the safety of these medications.


4 sources
  1. FDA's List of Tainted Weight Loss Products (33)
    Source link
  2. Cardiovascular risk-benefit profile of sibutramine
    Source link
  3. Questions and Answers about FDA's Initiative Against Contaminated Weight Loss Products
    Source link
  4. Liver Injury from Herbal, Dietary, and Weight Loss Supplements: a Review
    Source link
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Written by:

Rabia Khaliq

MSc in Applied Psychology

Dr. Bradley Noon



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Evidence Based

This article is based on scientific evidence, written by experts and fact checked by experts.

Our team of experts strive to be objective, unbiased, honest and to present both sides of the argument.

This article contains scientific references. The numbers
in the parentheses (1, 2, 3) are clickable links to peer-reviewed scientific papers.