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What Is Drug Tolerance?

Learn about drug tolerance, the negative side effects and risks, and resources available that can help.

Tolerance and Addiction

Drug tolerance can be a common occurrence in those who struggle with addiction. However, despite misconceptions, tolerance to a drug and addiction are not the same thing. Understanding substance tolerance is an important part of addiction treatment to provide patients with the best possible care.  

Drug Tolerance Definition

Drug tolerance is when someone’s body or brain no longer responds to a drug the way it once did. Building a tolerance to drugs can cause an addiction to occur or worsen the symptoms of an already existing addiction.1

How Does Drug Tolerance Work?

When tolerance to drugs occurs, someone will have to take higher doses of a drug to receive the same effects they once did. Tolerance to a drug can occur when someone takes a prescription medication at recommended doses. This is also referred to as drug insensitivity where someone has a reduced reaction to a drug after repeated use. 

Increasing Doses

Drug insensitivity to prescription medication will cause a doctor to have to up the dosage or switch someone to a new medication so they can continue treating a medical condition.

When someone with an addiction builds a substance tolerance, they will likely begin taking increasingly higher doses of the drug to receive the same effects or may begin combining the drug with other substances to create a stronger high. Taking higher doses or combining substances is extremely dangerous and can lead to life-threatening health complications, such as a drug overdose.

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Drug Tolerance vs. Drug Dependence

The main difference between tolerance and dependence is that tolerance has to do with the effectiveness of a drug, whereas dependence has to do with the body or mind becoming reliant on taking a substance.  

Tolerance to a drug requires taking higher doses of a substance to keep receiving the same effects. Dependence on a drug causes physical withdrawal symptoms if you stop taking it or makes you feel like you can’t function normally without it. 2

Drug Tolerance Causes and Risk Factors

There are many different causes and risk factors that can contribute to developing substance tolerance.

What Causes Tolerance to Drugs?

The main cause of tolerance is taking a drug repeatedly over an extended period of time. The body begins to adapt and can process the drug more quickly. This leads to needing to take a higher dose of a substance to continue feeling the effects.

Drug Tolerance Risk Factors

Common risk factors of drug tolerance are:

  • Age: Someone’s age can impact their metabolic rate and how quickly they are able to process a substance. This can lead to individuals who are younger or older being more prone to developing a tolerance, depending on the type of substance. 
  • Sex: Certain drugs can be more prone to developing a tolerance for males or females based on certain biological factors and how the drugs affect the body differently for people of different genders. 
  • Weight: Those who are heavier will likely have to take higher doses of drugs to receive the same effects. 
  • Underlying mental conditions: Mental health conditions can impact drug use and the development of tolerance to drugs. Those who have underlying mental health conditions may be more susceptible to abusing drugs at high doses which leads to substance tolerance. 
  • History of substance use: Someone with a history of substance use will also be more likely to develop a tolerance if they have taken drugs repeatedly for a long period of time. 

Different Types of Drug Tolerance

There are different types of drug tolerance that may occur. Treatment for addiction and tolerance may vary depending on the type of tolerance to a drug that someone has.


Tachyphylaxis occurs when a medication suddenly provides a lessened effect than what it once did. This is common in medications for depression or eye drops for redness relief. Health care providers usually recommend switching medications or upping the dosage when a tachyphylaxis tolerance to medication occurs. 3

Pharmacodynamic Tolerance

Pharmacodynamic tolerance occurs when the brain chemistry adapts to the presence of a drug. This type of tolerance is common in drugs that are used to modify the brain activity in certain neurotransmitters.4

Pharmacokinetic (Metabolic) Tolerance

A pharmacokinetic tolerance, also known as a metabolic tolerance, is when the body’s metabolic system begins to process a drug quicker when someone takes it for an extended period of time. Since the body processes the drug faster, it leads to diminishing effects of the substance.

Behavioral Tolerance

Behavioral tolerance is when someone adapts to being able to partake in daily activities while taking a substance. Behavioral tolerance leads to frequent drug use behavior such as using drugs on the job or drinking alcohol or taking drugs before driving.

Health Effects and Risks of Drug Tolerance

There are many risks associated with building a tolerance to drugs. Some risks of tolerance can be extremely dangerous and can have lifelong health effects. Some of the risks are:

Drug Addiction

One of the main risks of tolerance is developing a drug addiction. Tolerance causes someone to continue taking high doses of a substance. Taking high doses of drugs repeatedly will make someone more susceptible to addiction.


When someone develops a tolerance to one drug, they may also develop a tolerance to other drugs that have similar chemical properties. This is known as a cross-tolerance to a drug. Cross-tolerance to drugs can be harmful when being treated for medical conditions since many substances may be ineffective for treating a patient.

Mental Health Conditions

Tolerance of drugs can also impact mental health conditions. Taking high doses of substances can worsen existing mental health issues or cause mental health issues to occur.

Chronic Pain

Tolerance to a drug can also impact chronic pain. Those who struggle with chronic pain may receive fewer benefits from painkillers due to developing a tolerance. The side effects of taking high doses of a substance can also cause chronic pain to occur or may cause chronic pain as a withdrawal symptom if you suddenly stop taking an addictive substance.

Seizure Disorders

Tolerance to drugs can also impact people who struggle with seizure disorders or may cause seizures to occur as a side effect of taking high doses of a substance.

Immune-Related Conditions

Drug tolerance can cause a weakened immune system over time. This is due to how high doses of drugs affect the body and the body’s natural ability to fight off disease and infections.


One of the more dangerous side effects of tolerance is overdose. Taking high doses of a substance due to having a drug tolerance is dangerous and makes someone more susceptible to overdosing. This is due to the severe side effects that many substances can have when taken excessively.

Treatment for Drug Tolerance

If you or someone you know is struggling with addiction or drug tolerance, there are resources available. Seeking treatment from a drug treatment center is the best way to get on the path to recovery.

How to Prevent Drug Tolerance

The best way to prevent drug tolerance is to only take medications within the recommended guidelines of your health care provider. Be sure to ask them questions about the side effects and dosage so you know how to take the medication safely.

Using Psychotherapy as a Supportive Care

Psychotherapy can be an effective treatment method for those who struggle with a dual diagnosis of drug addiction or tolerance, along with a mental health condition. Psychotherapy is an effective method of treating mental health issues and can also help patients work through addiction as well.  

A psychotherapist will help you learn about how your moods, thoughts, and behaviors are affecting your condition and will teach you healthy coping methods.

Call Ripple Ranch Recovery Today for Help

If you are looking for treatment for drug tolerance or addiction, Ripple Ranch Recovery can help. Ripple Ranch Recovery is a treatment center that uses evidence-based treatment methods to get you the best possible results.

The knowledgeable professionals at Ripple Ranch Recovery can help you create a personalized recovery plan and will be with you every step of the way as you work through a treatment program. Call us today for more information on how we can help.