Anabolic-androgenic steroids (AAS) are a synthetic form of testosterone used to increase muscle mass and strength. They may be dangerous and cause side effects, and the risks generally outweigh any benefits.

To increase muscle strength and power beyond the natural limit, some people turn to substances like anabolic-androgenic steroids (AAS).

Anabolic refers to growth promotion, whereas androgenic refers to the development of male sex characteristics.

While steroids’ muscle-building capabilities are well documented, they come with several potential side effects.

This article reviews anabolic-androgenic steroids, including their uses, side effects, dangers, and legal status.

Anabolic-androgenic steroids (AAS) are a synthetic form of testosterone, which is the primary male sex hormone (1).

They affect various parts of your body, such as your muscles, hair follicles, bones, liver, kidneys, and reproductive and nervous systems.

Humans naturally produce this hormone.

In men, its levels increase during puberty to promote the development of male sex traits, such as body hair growth, a deeper voice, sex drive, and increased height and muscle mass.

Though traditionally thought of as a male hormone, women also produce testosterone but in much smaller amounts. It serves several functions for women, primarily promoting bone density and a healthy libido (2).

Normal testosterone levels range from 300–1,000 ng/dL for men and 15–70 ng/dL for women. Taking steroids raises levels of this hormone, which causes effects such as increased muscle mass and strength (3, 4).


Steroids are a synthetic form of testosterone, a sex hormone naturally produced by men and women alike. Taking steroids increases testosterone levels, causing effects like increased muscle mass and strength.

When you think of steroids, the first thing that may come to mind is their use in bodybuilding to promote muscle gain. While this is a common application, AAS are used for several other purposes.

The main potential benefits associated with anabolic steroids are the following(1):

  • increases in muscle tissue due to enhanced protein synthesis
  • decreased body fat percentage
  • increased muscle strength and power
  • enhanced recovery from workouts and injury
  • improved bone mineral density
  • better muscle endurance
  • increased red blood cell production

These potential effects may benefit various groups of individuals.

Athletes looking to improve speed and power output

In the world of sports, athletes are constantly looking for ways to get an edge over the competition.

While advanced strength and conditioning exercises, as well as nutrition, go a long way in this regard, some athletes take it a step further by taking performance-enhancing drugs (PEDs).

AAS are one of the major PEDs used by athletes. They have been shown to increase muscle mass, which leads to increased speed and power output (5).

Athletes using AAS can experience strength gains of 5–20% and weight gains of 4.5–11 pounds (2–5 kg), which may be due to an increase in lean body mass (5).

In competitive sports, steroid dosing tends to be fairly conservative to avoid detection. Muscle mass is not the main concern here, as they’re used more for recovery and increased power output (6, 7).

Though most sporting federations ban AAS, some athletes feel the risk of getting caught is worth the benefits.

Strength athletes looking to increase muscle mass and strength

When it comes to strength sports, including bodybuilding, powerlifting, and Olympic weightlifting, anabolic steroids are widely used to increase muscle mass, strength, and power output (5).

In these sports, muscle strength, size, and power directly relate to overall performance.

While the goal of bodybuilding is maximum muscle mass in a given category, strength and muscle size are closely related, though other factors are at play as well (8).

The dosing of AAS in strength sports tends to be more liberal, as many federations don’t test for these and other substances. While more potent effects may be seen at higher doses, the risk of side effects increases as well.

Many users in this category also utilize a strategy called “stacking,” which is a slang term for mixing multiple types of AAS. Some athletes also include other synthetic hormones, such as growth hormone and insulin.

Those with muscle-wasting diseases

Several conditions can lead to muscle loss, including AIDS, chronic obstructive pulmonary disease (COPD), cancer, and kidney and liver disease. While not as common, AAS can be used in these populations to help preserve muscle mass (9, 10).

Loss of muscle mass has been closely linked to mortality in these diseases and preventing it can improve therapeutic outcomes and extend lifespan (11, 12, 13, 14).

While AAS use is not the only method to preserve muscle mass, it may benefit these populations. Still, potential side effects must be taken into consideration.


Common uses for steroids include improving performance in athletics, increasing muscle mass in strength athletes, and preserving muscle mass in those with muscle-wasting diseases.

Despite their potential benefits, AAS have several possible side effects, whose severity varies depending on the extent to which you use these substances.

Individual genetics also affect how you respond to AAS (15).

The anabolic-to-androgenic ratio varies between different types of AAS, which may affect adverse reactions as well. Anabolic refers to muscle growth properties, whereas androgenic refers to the promotion of male sex traits (16).

The main side effects associated with AAS use are the following:

  • Increased risk of heart disease. AAS used in combination with resistance exercise can increase the size of the left ventricle of your heart, as well as blood pressure. This may increase your risk of heart disease and related death (17).
  • Can increase aggressive behavior. Steroid use has been associated with increased aggression and impulsivity in male teenagers and adults (18).
  • Can affect body image. AAS use and dependence are classified as a body image disorder in the diagnostic manual for mental disorders (19).
  • Can cause liver damage. AAS, specifically those taken orally, have been shown to increase your risk of liver dysfunction (20).
  • May cause gynecomastia. Defined as swollen male breast tissue caused by a hormone imbalance, gynecomastia may occur when you stop taking AAS (21).
  • Decreased production of testosterone. Steroid use is associated with hypogonadism, which is characterized by the shrinking and decreased function of the testes (22).
  • Can cause infertility. Due to its potential to decrease sperm production, steroid use may cause infertility (23).
  • May cause male pattern baldness. The androgenic effects of AAS may cause or worsen male pattern baldness. This effect may vary depending on the specific drug used (24).

Side effects for women

While the above side effects can occur in men and women alike, women should be aware of additional ones, including (25, 26):

  • deepening voice
  • facial changes and hair growth
  • enlarged clitoris
  • irregular menstrual cycles
  • decreased breast size
  • infertility

Steroid use is associated with several adverse effects, such as an increased risk of heart disease and liver toxicity. Additional side effects are seen in women who use AAS.

AAS use comes with several risks, making them potentially dangerous for most people. While certain methods can minimize some of these risks, they cannot be fully avoided.

Frequent blood work is important

AAS use can affect several lab values, making frequent blood work important to avoid major complications. Steroid use can affect the following lab values (27, 28):

  • Can increase hemoglobin and hematocrit. These blood markers play an important role in oxygen delivery throughout your body. Increased levels can thicken your blood and increase your risk of heart attack and stroke.
  • Can reduce HDL (good) cholesterol and raise LDL (bad) cholesterol. HDL and LDL cholesterol should be within healthy ranges. Lower HDL and higher LDL levels may increase heart disease risk.
  • Can increase liver markers. AAS use has been associated with increased aspartate transaminase (AST) and alanine transaminase (ALT), two markers of liver function. Elevated levels may indicate liver dysfunction.

You should consult your medical provider before beginning a regimen that alters your body’s natural hormone levels.

Risk of infection

When taking AAS, the risk of infection can be fairly high. This is because many steroids are produced in illegal labs that don’t follow the same procedures as commercial labs.

For steroids that must be injected, there is an increased risk of contamination and infection.

When procuring AAS on the black market, there is a chance of mislabeled or counterfeit substances, further increasing your risk of infection.

Illegal in most places

The legal status of AAS varies by country and region, though they’re classified as illegal in most places if used for non-therapeutic purposes.

Anabolic steroids are classified as a schedule III drug in the United States. Illegal possession can carry a maximum penalty of 1 year in prison and a minimum $1,000 fine for the first offense (29).

The only way to obtain and use AAS legally would be to have them prescribed by a medical professional for a certain condition, such as low testosterone or a muscle-wasting disease.

People who choose to use them illegally put themselves at risk of legal consequences.

May be mentally addictive

Though AAS are not classified as physically addictive, continued use may be associated with mental addiction that can lead to dependence (30).

A common psychological side effect of AAS use is muscle dysmorphia, in which users become preoccupied with having a muscular physique (31).


Steroid use is dangerous for several reasons, including the high risk of infection, their illegal status in most places, and potential for mental addiction. Frequent blood work is essential to monitor potential negative health effects.

While lower, well-calculated doses of AAS can be significantly safer than uncontrolled doses associated with abuse, no studies have compared the safety of different steroid doses.

Synthetic testosterone is also used to treat individuals with low testosterone, which is referred to as testosterone replacement therapy (TRT).

TRT is generally safe for men with low testosterone levels when administered by a medical professional. Data to determine the safety of TRT for women is insufficient (32).

The higher doses commonly used in competitive athletics and strength sports are linked to an increased risk of side effects and cannot be deemed safe (1).

Regardless of the dose, taking AAS always has a level of associated risk.

People respond differently to AAS due to variations in genetic makeup. Therefore, it’s difficult to know exactly how your body will react.


While lower, controlled doses associated with testosterone replacement therapy are generally accepted as safe for men with low testosterone, taking steroids in any amount can pose health risks. More serious side effects are seen with higher doses.

While AAS are the most commonly talked-about type of steroid, there is another variety called glucocorticoids or corticosteroids. These are naturally occurring hormones produced in the adrenal glands located on top of your kidneys (33).

They serve as a feedback mechanism in your immune system, which regulates inflammation. Synthetic versions are often used to treat certain conditions caused by an overactive immune system, including:

  • allergies
  • asthma
  • autoimmune diseases
  • sepsis

While they work well to regulate certain illnesses, they can cause several side effects, such as elevated blood sugar levels and weight gain. For this reason, they’re reserved only for moderate to severe inflammatory conditions (34).


Corticosteroids are another type of steroid naturally produced in your body to help regulate inflammatory immune processes. Synthetic forms are used to reduce inflammation in many autoimmune diseases.

Anabolic-androgenic steroids (AAS) are a synthetic form of testosterone used to increase muscle mass and strength.

While their health risks vary by the type and amount taken, they can be dangerous and cause side effects at any dose. Plus, they’re illegal in most places.

Using AAS is a very serious decision, and the risks generally outweigh any benefits.