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Are Diet Pills a Controlled Substance?

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Why are most diet pills classified as controlled substances by the Drug Enforcement Administration (DEA)?  

You may feel like you’ve tried everything to lose weight. You’ve spent some time following a reduced-calorie diet, increased physical activity, and still have not seen any results. It could be time to call your doctor and see if they can prescribe you something that can help. Be careful, you may be increasing the risk of complicating your situation even further.

Many diet pills are meant for chronic weight management, but contain ingredients that may be habit-forming, and have a high potential for abuse. To prevent their abuse, the DEA categorizes them into different controlled substance schedules. Active drugs in most weight loss pills are similar to amphetamines (stimulants). 


Long-term abuse of these drugs may cause:


What are Diet Pills?

Diet pills are prescription weight loss medications. Some people call them anti-obesity medication. Though commonly called diet pills, some of them are available only by injection. 

Your doctor may prescribe these medications if you have:

  • Serious health issues because of excess body weight. 
  • Not lost significant weight with diet and exercise. 

Notably, diet pills should be used with – not as a replacement for – diet and exercise. 


What is a Controlled Substance?

As per the Controlled Substances Act (CSA), the DEA categories substances into one of the five schedules based on their:

pills and a measuring tape

  • Accepted medical use in the U.S.
  • Abuse potential
  • Safety
  • Risk of producing dependence
  • History and current pattern of abuse
  • Risk to public health


Five Controlled Substance Schedules


1. Schedule I Controlled Substances

These substances have no medical use, no accepted safety, and high abuse potential.


  • Heroin
  • LSD
  • Cannabis
  • Peyote
  • Methaqualone
  • Ecstasy


2. Schedule II/IIN Controlled Substances (2/2N)

These substances have high abuse potential and may cause severe psychological or physical dependence. This schedule includes potent narcotics (opioids) and stimulants.  


  • Hydromorphone (Dilaudid) 
  • Methadone  (Dolophine)
  • Meperidine (Demerol)
  • Amphetamine (Adderall) 
  • Methylphenidate (Ritalin) 
  • Amobarbital
  • Glutethimide


3. Schedule III/IIIN Controlled Substances (3/3N)

These substances are less likely to be abused than those in Schedules I or II. They may cause moderate or low physical dependence or high psychological dependence.



4. Schedule IV Controlled Substances

These substances have low abuse potential compared to Schedule III substances.


  • Alprazolam (Xanax)
  • Clonazepam (Klonopin) 
  • Diazepam (Valium)
  • Lorazepam (Ativan)
  • Midazolam (Versed)
  • Temazepam (Restoril)
  • Triazolam (Halcion)


5. Schedule V Controlled Substances

These substances have low abuse potential compared to Schedule IV substances.


  • Cough preparations with Codeine (Robitussin AC, Phenergan with Codeine) 
  • Ezogabine.

diet pill schedule level infographic

FDA-approved Weight Loss Medications and their Schedules

doctor and patient

Medications for long-term use

The United States FDA has approved the following drugs for long-term treatment of overweight and obesity. 

  1. Orlistat (Xenical, Alli): Orlistat is not a controlled substance. It means its use is unlikely to cause psychological or physical dependence. 
  2. Lorcaserin (Belviq): Lorcaserin is Schedule IV controlled substance. This medication has a low abuse potential compared to Schedule III substances, such as buprenorphine (Suboxone).  

The manufacturer of Lorcaserin (Belviq), Eisai Inc., voluntarily withdrew this drug from the U.S. market in 2020. If you have been taking this medication, stop immediately. Ask your provider if alternative medicines are appropriate.


  1. Phentermine-topiramate (Qsymia): Qsymia falls in Schedule IV of the Controlled Substances Act. It is because this medicine contains phentermine, a Schedule IV drug
  2. Naltrexone-bupropion (Contrave): Contrave is not a controlled substance.
  3. Liraglutide (Saxenda): Saxenda is not a controlled substance.


Medications for short-term use (up to 3 months)

  1. Phentermine (Suprenza) and Diethylpropion (Tenuate): Schedule IV controlled substance.  
  2. Benzphetamine (Didrex) and Phendimetrazine (Adipose, Anorex-SR, Statobex)Schedule III controlled substance. These medicines have a higher risk for abuse than Qsymia and Belviq. Moderate or low physical dependence or high psychological dependence is possible with their use.


Important Facts, Medication Guide

Safe use

  • Consult your doctor if you have heart disease, mood disorders, liver or kidney disease, or a history of stroke. 
  • Avoid stopping use without talking to your doctor or pharmacist. 
  • Some diet pills may interfere with vitamin absorption. Consider taking a multivitamin supplement. 



For Schedule III or IV substances, 

  • The DEA does not allow filling or refilling a prescription if more than six months have passed since the prescribed date.
  • The DEA prohibits refilling more than five times. 


Storage and disposal

  • Keep in a tightly closed container. 
  • Avoid storing your medicines within your child’s sight and reach. 
  • Store it at 20 to 25°C (68 to 77°F). 
  • Do not store your medicines in the bathroom. 
  • Check if your community has drug take-back programs.
  • Check the United States FDA-approved list of medicines for disposal by flushing.  


Key Takeaways

  • Some diet pills may be habit-forming. 
  • Long-term abuse may cause severe symptoms, including psychosis and psychological dependence.  
  • Prescription weight loss pills fall into one category: not controlled, Schedule III controlled substance or Schedule IV controlled substance. 
  • Schedule III: Benzphetamine and Phendimetrazine.
  • Schedule IV: Phentermine-topiramate, Phentermine, and Diethylpropion.
  • Drugs in Schedule III are more likely than those in Schedule IV to cause drug dependence. 


What is the most potent weight loss prescription pill?

Qsymia is probably the most potent prescription pill used to lose weight. The other two pills in the top three list are Saxenda and Contrave. On average, 75% of participants using Qsymia, 63% using Saxenda, and 55% using Contrave lost 5% of their weight, respectively. 


Why is Phentermine a controlled substance?

Phentermine is a Schedule IV controlled substance. A dose of qsymia may cause dependence comparable to alprazolam (Xanax), clonazepam (Klonopin), and diazepam (Valium). 


Does phentermine show on a drug test?

Phentermine is similar to amphetamines. Using phentermine may lead to a false-positive urine test for amphetamines.


What diet pill is the same as phentermine?

Phentermine is available in different brands. These include:

  • Adipex-P
  • Atti-Plex P
  • Fastin
  • Ionamin
  • Phentercot
  • Phentride
  • Pro-Fast


Is Phentermine a Narcotic?

Phentermine is not a narcotic. Narcotics act on opioid receptors and are used to treat moderate to severe pain. Phentermine is a stimulant. It stimulates norepinephrine and epinephrine release and suppresses appetite.

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