What Happens When You Use Heroin?

Over the last 20 years, heroin addiction has entered the national spotlight as one of the leading causes of preventable death in the United States. This is due to its potency as well as the variety of neurological effects it produces. In this article, we take a detailed look at how heroin affects the brain and body immediately upon using it.

Related Articles: Heroin Withdrawal Guide | Dangers of Heroin Abuse | Heroin Addiction Treatment | Short & Long Term Effects of Using Heroin | Signs and Symptoms of Heroin Addiction

How Heroin Affects The Brain

When heroin is present in the brain, the body will respond by decreasing the production of natural opioids. This initially produces tolerance, but once heroin has been used for an extended time, usually several weeks, this will result in dependence upon heroin. This means that the brain will be unstable without continued heroin use and withdrawal symptoms will begin to appear if someone goes too long without using. Without the continued introduction of heroin, withdrawal symptoms will start to appear.

Heroin produces its effect by hijacking the natural opioid system of the brain. This system is used to mediate pain, reduce depression and anxiety, and produce feelings of reward. Our bodies make natural chemicals that stimulate this system known as “endogenous” opioids. Heroin acts on some of the same receptors as these endogenous opioids, however, heroin activates these opioid receptors much more strongly than the opioids produced by the body. This can have very far-reaching effects throughout the body.

Sensory Effects

The most potent effect of heroin is on the perception of pain. This is most directly produced by heroin’s interaction with the μ-opioid receptors in the brain. Due to the strength with which heroin activates the opioid receptors, the perception of pain is greatly dulled. Heroin can also dull the perception of any other uncomfortable stimulus including cold, anxiety, tension, and physical discomfort of any kind. This means that any sensation of pain or discomfort will be weakened, or not even perceived at all. 1

Emotional Effects

Heroin use not only produces positive feelings of calm and relaxation, but it also reduces negative emotions. Feelings of anxiety or depression are decreased or eliminated entirely while simultaneously a great sensation of wellness, security, and peace is produced. Once the brain has adapted to this state, removing heroin will have the opposite effect and these feelings will strongly rebound, increasing depression and anxiety above their pre-heroin levels.

Behavioral Effects

Heroin is a very strong depressant, and it can make cause someone to have very low energy levels. One of the most noticeable behaviors that people exhibit when using heroin is frequent itching and “nodding off”. This is a small lapse in consciousness that may look like someone has suddenly fallen asleep. People will often lay around for hours on end while high on heroin, drifting in and out of consciousness no matter what is going on around them.

How Heroin Affects The Body

Heroin also affects a wide variety of systems in the body. Since heroin is a powerful depressant, this means that everything gets slowed down to some degree. This can affect many different areas, including brain function, heart rate, breathing, and digestion. For a closer look, let’s examine each system in turn:

Cardiovascular Effects

Heroin produces several effects on the heart and circulatory system. Heart rate slows which lessens the speed that blood will circulate and replenish oxygen or remove waste. This has a cascade on all other vital functions, as oxygen-rich blood is required by every cell in the body. Blood pressure will also decrease, which can lead to poor circulation in the extremities and create the possibility of getting lightheaded or fainting when standing suddenly. Furthermore, many long term heroin users exhibit irregular heartbeats due to chronic inflammation, scarring, and fatty tissue buildup in and around the heart. IV heroin use poses the added risks of collapsed veins, abscesses, bacterial infections, and heart infections.

Pulmonary Effects

The depressant effects of heroin are most visible in someones breathing. Immediately after use, there will be a sharp decrease in the number of breaths someone takes per minute. This is due to a decrease in signals to the diaphragm from the brain and is the leading cause of death in heroin overdoses. An overdose victim can die of hypoxic brain damage more readily than heart failure. Furthermore, there are a number of lung issues caused by IV heroin use which may be painful, debilitating, or even fatal. Some of these include pulmonary embolism, pneumonia, and tuberculosis.

Gastrointestinal Effects

Aside from the possibility of nausea and vomiting, the rest of the lower gastrointestinal tract is affected as well. Heroin use causes semi-paralysis of the large and small intestines which greatly reduces digestion speed and bowel movement frequency. In chronic heroin users, constipation is extremely common with the bowel movements themselves being very difficult to pass. This slowing of function can lead to reduced and slowed nutrient absorption and this can have a direct effect on immune function and overall health. The strain put on the rectum and intestines can also lead to hemorrhoids, prolapse, or hernia. The liver and kidneys also have great strain put on them by heroin use since the liver metabolizes heroin and filters the blood from the GI tract, while the kidneys are responsible for blood filtration and waste excretion in urine. Heroin use will only add to their workload, and any contaminants or cutting agents may be dangerous or even toxic.

Reproductive Effects

Heroin use has severe effects on reproduction in both men and women, however, these effects differ in nature:

  • Male Reproduction: In men, heroin makes it difficult or impossible to ejaculate while someone is high on the drug. After prolonged use, blood testosterone levels are reduced as well as sperm motility (ability to swim) being impaired while sperm quantity is also decreased. These effects on testosterone and sperm are known to persist long after heroin use has been discontinued. 2
  • Female Reproduction: In women, heroin is known to cause a wide range of menstrual abnormalities as well as amenorrhea, or a lack of menstruation. This may take many months or years to resolve after heroin use has stopped. Additionally, heroin use can severely decrease sex drive in women. 3
  • During Pregnancy: Using heroin while pregnant poses a wide range of serious risks for both the fetus and the mother. The risk of maternal death is elevated as well as the risk of premature birth or stillbirth, miscarriage, specific birth defects, and neonatal abstinence syndrome. Babies born to mothers who abused heroin often have low birth weight and also show irregular breathing patterns, particularly while sleeping. Additionally, there is a 5-10x increased risk of sudden infant death syndrome, as well as higher mortality in general for infants born to mothers who used heroin. 4, 5, 6


  1. Hawai’i Medical Journal: Understanding Endorphins and Their Importance in Pain Management
  2. Trends in Urology & Men’s Health: Recreational Drugs and Male Fertility
  3. U.S. Department of Health and Human Services: Substance Abuse Treatment – Addressing the Specific Needs of Women
  4. U.S. Department of Health and Human Services: Pregnancy and Opioid Pain Medications
  5. Centers for Disease Control: About Opioid Use During Pregnancy
  6. Fertility and Sterility: Drug Abuse and Reproduction

Heroin Addiction Resources

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