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Side Effects of Codeine: Common & Rare Risks to Look For

Peter Manza, PhD profile image
Reviewed By Peter Manza, PhD • Updated Aug 13, 2023 • 7 cited sources

Codeine is a prescription painkiller often used for moderate pain. While painkillers are dangerous, they’re also common. In 3.6% of American counties, enough prescriptions for drugs like codeine were dispensed to enable every resident to have one.[1]

Taking codeine as prescribed has some risks. The drug has several known side effects, including some that are lethal. But misusing the drug can cause even more problems. 

What Are the Common Side Effects of Codeine?

Opioids latch to receptors in the brain and body, triggering chemical reactions that can make pain easier to ignore. Few people can take codeine without noticing at least some type of side effect.

The most common codeine side effects include the following:[2]

  • Constipation
  • Dizziness
  • Drowsiness
  • Lightheadedness
  • Sedation
  • Shortness of breath
  • Sweating 
  • Nausea
  • Vomiting

Most of these problems are dose dependent, meaning they get stronger with higher amounts consumed. But even a small pill could make you feel sick or uncomfortable.

What Are Rare or Uncommon Codeine Side Effects?

Some people experience more significant side effects due to their codeine doses. While these problems are rare, they can be serious. 

Known uncommon but dangerous codeine side effects include the following:[2]

  • Abdominal pain or cramping
  • Anorexia
  • Anxiety
  • Confusion
  • Diarrhea
  • Fainting
  • Heart palpitations
  • Insomnia 
  • Itchy skin
  • Nervousness

If your doctor prescribes codeine and you develop these side effects, notify your medical team. The medication may not be safe for you to continue.

Dangerous Codeine Interactions 

Codeine is a central nervous system depressant, capable of slowing your breathing and heart rates.[3] Drugs like this can place you into a sedated state. Taking them alongside other medications could make the problem worse.

Codeine is known to interact with the following types of medications:[2]

  • CNS depressants: Antihistamines, antipsychotics, alcohol or other medications that slow your breathing cause life-threatening complications when mixed with codeine. 
  • Opioid agonists: Medications like Suboxone render codeine inactive, forcing you into abrupt withdrawal symptoms immediately. 
  • Antidepressants: MAO or MAOI medications mixed with codeine can interfere with how quickly your body metabolizes opioids. 

If you’re using one of these medications and your doctor prescribes codeine, talk about the risks. It’s probably not safe for you to use both, and your doctor can help you make smart choices.

If you’re using these medications and considering misusing codeine, think again. It’s not safe for you to mix drugs like this. 

Codeine Risks & Warnings

Common drugs may seem safe. If you know someone who used codeine without problems (and most people do), you may believe it’s incapable of causing harm. In reality, codeine is very dangerous, even for people using the drug with a valid prescription from a doctor.

These are risks and warnings that apply to anyone who uses codeine, including those following a doctor’s orders. 

Physical Dependence

Chemical changes caused by codeine are persistent. Your brain cells release large amounts of neurotransmitters each time you take a pill. Responders become numb to the flood of chemicals, and in time, they rely on them. 

When your cells no longer function properly without codeine, you’ve developed a physical dependence. Researchers say the odds of a person developing opioid dependence goes up sharply after just 5 days of use.[4]

When you’re physically dependent on codeine, you may feel sick between doses. In time, you may begin taking your doses close together in time, or you may transition to stronger medications (like Vicodin or heroin) to keep sickness at bay.

Physical dependence is a natural response to codeine’s constant presence. You can be dependent on drugs and not addicted to them. But without help, dependence can transition into opioid use disorder (OUD).


Researchers define misuse as using a medication via a method your doctor didn’t authorize. Using too much of a drug, taking doses too close together or buying drugs from dealers all constitute misuse. 

A national survey found that 9.7 million people misused prescription painkillers like codeine in 2019.[5] The longer you take the drug, the more likely you are to do the same. 

As your physical dependence deepens, you will need more codeine to stave off sickness. Misusing your prescription may seem like the most effective way to feel like yourself. If you’re unable to get more codeine, you may turn to other opioids like other forms of prescription painkillers or heroin.


People with opioid use disorder put codeine at the center of everything they do. You may let work, family and friend obligations slide to make more room for drugs. And you may risk your reputation, personal safety and future to keep your drug use alive. This becomes the main priority in your life.


In one 12-month period, about 108,000 people died due to drug overdoses, and about 75% of them involved opioids like codeine.[6] An OUD can blind you to the risks involved with taking large amounts of drugs, and in time, your doses could overwhelm your central nervous system and stop your breathing. An overdose is a very serious consequence of opioid use and misuse.

Getting Help for OUD

In a Medication for Addiction Treatment (MAT) program, doctors use opioid agonist medications like Suboxone to correct chemical imbalances. Medications like this can ease withdrawal sickness, so you can get sober without enduring life-threatening complications. Continued use can ensure you don’t relapse to codeine misuse.

Researchers say MAT, which may last indefinitely, is the safest way to treat OUD.[7] Programs like Bicycle Health can help. 

Our telemedicine model means doctors treat you where you are via video chat. You complete appointments through your computer and pick up your medications at a pharmacy near you. This makes MAT care accessible for people all over the U.S., and it increases the likelihood that you’ll stick with treatment once you start. 

Contact us to find out more about how these programs work and find out if they’re right for you.

Reviewed By Peter Manza, PhD

Peter Manza, PhD received his BA in Psychology and Biology from the University of Rochester and his PhD in Integrative Neuroscience at Stony Brook University. He is currently working as a research scientist in Washington, DC. His research focuses on the role ... Read More

  1. U.S. Opioid Dispensing Rate Maps. Centers for Disease Control and Prevention. November 2021. Accessed April 2023.
  2. Codeine Prescribing Information. U.S. Food and Drug Administration. April 2013. Accessed April 2023.
  3. What are opioids and why are they dangerous? Mayo Clinic. March 2018. Accessed May 2023.
  4. Opioid Dependence Can Happen After Just 5 Days. Truth Initiative. October 2018. Accessed April 2023.
  5. Heroin and Opioid Awareness. U.S. Attorney's Office, District of Nevada. August 2022. Accessed April 2023.
  6. Opioid Use Disorder. American Psychiatric Association. December 2022. Accessed April 2023.
  7. The Effectiveness of Medication-Based Treatment for Opioid Use Disorder. Medications for Opioid Use Disorder Save Lives. March 2019. Accessed April 2023.

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