What Are Effects of Heroin?

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Heroin is a potent, illegal drug sold as a white or brownish powder or as a dark, sticky substance known as “black tar heroin.”1

Heroin can be injected, smoked, or snorted to produce a euphoric high. Its powerful effects give it a high potential for addiction and overdose.

What Happens When You Use Heroin?

The onset and duration of heroin’s effects depend on the method of use. The quickest onset occurs with intravenous injection, and the slowest with subcutaneous injection (“skin popping”).2

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  • Intravenous injection: onset within 1-2 minutes, peak within 10 minutes.
  • Intramuscular injection: onset within 15-30 minutes, peak within 30 minutes.
  • Snorting: effects peak within 30 minutes.
  • Subcutaneous injection: effects peak within 90 minutes.

After the peak, the sedating effects of heroin can last up to an hour, with analgesic (pain relief) effects lasting between 3 and 5 hours.2 The effect that heroin has on a user can vary based on the user’s tolerance level, dose taken, and how it is used.

Effects on the Brain

Man resting head on arms

Once ingested, heroin is converted to morphine in the brain.3 The morphine binds to endogenous opioid receptors located throughout the brain and body, which can affect critical life processes such as breathing and heart rate.3

Some evidence shows that heroin use may damage white matter in the brain, which can harm decision-making, behavior regulation, and stress response.3

Users of heroin may quickly need more and more of the drug to achieve the same high. This effect is known as tolerance, and it paves the way for dependence or addiction. Once addicted, users are at risk for health problems or death by overdose.

Short-Term Changes

Heroin slows activity in the central nervous system and causes a reduced sensation of pain and a “rush” of good feelings, which is the high that users seek with repeated and prolonged use.

Heroin short-term effects include:3, 4

  • Warmth.
  • Euphoria or a “rush.”
  • Decreased perception of pain.
  • Heavy extremities.
  • Drowsiness.

Side Effects

Unfortunately, the rush from heroin comes with a host of uncomfortable and dangerous side effects. Heroin side effects include:3, 4

  • Dry mouth.
  • Itching skin.
  • Nausea and vomiting.
  • Slowed breathing.
  • Alternating states of drowsiness and alertness.
  • Decreased mental function.
  • Loss of consciousness.

Life-Threatening Repercussions

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When a person takes a dose of heroin that is too high for their body to handle, they are likely to experience overdose effects, which can be deadly. A person may overdose if they take a large dose or if they take a dose that is more potent than they are used to, perhaps because the heroin has been mixed with stronger opioids such as fentanyl.6

If heroin overdose is suspected, call 911 immediately. The overdosing individual needs professional medical help right away to prevent permanent damage and death.

Other life-threatening effects of heroin use include:4, 5

  • Breathing of stomach contents into the lungs while unconscious, causing choking, pneumonia, or death.
  • Prolonged vomiting and diarrhea (frequently occurs in heroin withdrawal), causing dehydration or electrolyte imbalances.
  • Reduced breathing, which can result in cerebral hypoxia and long-lasting brain damage.

Long-Term Effects

User experiencing long-term effects of heroin addiction

Long-term use of heroin often leads to a pattern of life-altering addiction. When a person suffers from a heroin addiction, they may struggle with relationship problems, occupational issues, major health problems, and self-motivation – often opting to use heroin instead of engaging in other things they once found enjoyable.

On top of these issues, a person struggling with long-term heroin abuse runs a high risk of incurring permanent brain damage (sustained over the course of numerous episodes of compromised breathing and a resultant lack of oxygen); long-term alterations in hormonal functioning, which can affect sexual functioning; and a general reduction in their ability to control impulses and behaviors.7, 8

Those who snort heroin may also incur damage to the nasal passage that is similar to what occurs with the use of other insufflated drugs such as cocaine.8

Heroin use during pregnancy can also impact the developing baby.3 Heroin use can lead to poor prenatal care, and fetal heroin exposure has been linked to low birth weight and neonatal abstinence syndrome, an infant withdrawal syndrome that requires intense hospital care.3

Heroin long-term effects can be very dangerous for the user and include:3, 7, 8

  • Tolerance (a diminished response to heroin that ultimately requires a higher dose to achieve the same effect).
  • Dependence or addiction (represents the body’s physical need for heroin).
  • A severe withdrawal syndrome.
  • Long-term hormonal imbalance.
  • Impaired decision-making.
  • Impulsivity.
  • Poor response to stress.
  • Chronic, severe constipation; potential for intestinal obstruction or perforation.
  • Liver or kidney damage.
  • Pulmonary problems such as pneumonia.

Long-Term Effects of Injection

Injection is one of the most dangerous methods of heroin use because it introduces the effects of the drug the strongest and the fastest of all the routes of administration. The intensely rewarding rush that intravenous injection of heroin brings may also increase the user’s risk of addiction.7 Many users share their needles, which can lead to the transmission of blood-borne viruses that can threaten the user’s life.9 If the user is pregnant, she may pass these contracted diseases on to her baby, further increasing the risks associated with heroin use during pregnancy.3

Heroin use via injection has been associated with:3, 9

  • Vascular inflammation.
  • Collapsed veins.
  • Bacterial infections.
  • Abscesses at the injection site.
  • Infections of the heart lining and valves.
  • Hepatitis B or C.

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[1]. National Institute on Drug Abuse. (2014). What is heroin and how is it used?

[2]. Medscape. (2016). Heroin Toxicity.

[3]. National Institute on Drug Abuse. (2014). DrugFacts: Heroin.

[4]. National Institute on Drug Abuse. (2014). What are the immediate (short-term) effects of heroin use?

[5]. U.S. National Library of Medicine. (2016). Opiate and opioid withdrawal. Medline Plus.

[6]. Drug Enforcement Administration. Fentanyl.

[7]. National Institute on Drug Abuse. (2014). What are the long-term effects of heroin use?

[8]. National Institute on Drug Abuse. (2014). What are the medical complications of chronic heroin use?

[9]. National Institute on Drug Abuse. (2014). Why does heroin use create special risk for contracting HIV/AIDS and hepatitis B and C?

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