PEDs, or performance-enhancing drugs, are substances and methods athletes use to artificially boost strength, speed, endurance, or recovery beyond what training alone can achieve. The term covers a wide range of compounds, from anabolic steroids and hormones to stimulants and even blood transfusions. The World Anti-Doping Agency (WADA) maintains an official Prohibited List that currently includes over a dozen categories of banned substances and methods, updated annually.
Major Categories of PEDs
Not all PEDs work the same way. Some build muscle, others increase oxygen delivery, and some simply help athletes hide the evidence of using something else. WADA groups banned substances into several main categories:
- Anabolic agents (steroids and related compounds that build muscle)
- Peptide hormones and growth factors (substances like human growth hormone and EPO)
- Stimulants (compounds that increase alertness and reduce fatigue)
- Diuretics and masking agents (drugs that hide traces of other PEDs)
- Beta-2 agonists (bronchodilators that can also affect muscle growth)
- Hormone and metabolic modulators (drugs that alter how the body processes hormones)
- Prohibited methods (blood doping, gene doping, and physical manipulation of samples)
Some of these are banned at all times, both in and out of competition. Others, like stimulants, narcotics, and cannabinoids, are only prohibited during competition. Beta-blockers, which steady the hands and lower heart rate, are banned only in specific sports like archery and shooting.
How Anabolic Steroids Build Muscle
Anabolic steroids are synthetic versions of testosterone, the body’s primary male sex hormone. They’re the most well-known type of PED, and they work by ramping up the body’s muscle-building machinery in multiple ways simultaneously.
When steroids enter the body, they bind to receptors inside muscle cells and trigger those cells to produce more protein. This is the core of how muscle grows: more protein synthesis means more muscle fiber, especially when combined with resistance training. Steroids also activate satellite cells, which are essentially repair cells that fuse with damaged muscle fibers to make them larger and stronger. At the same time, steroids reduce the activity of genes involved in muscle breakdown, so the body is building more while losing less.
These effects happen through two pathways. One is slow, working over hours and days by altering which genes are turned on inside the cell. The other is fast, taking effect within minutes by activating signaling cascades that directly stimulate protein production. The combination makes steroids remarkably effective at increasing muscle mass and power output, which is precisely why they’ve been banned in competitive sports for decades.
EPO and Blood Doping
Erythropoietin, widely known as EPO, is a hormone your kidneys naturally produce when oxygen levels drop. It tells the body to make more red blood cells. In medicine, it treats severe anemia. In sports, athletes inject synthetic EPO to push their red blood cell count well above normal levels.
More red blood cells means more hemoglobin, the protein that carries oxygen from the lungs to working muscles. The result is a measurable increase in aerobic capacity. Studies show EPO boosts VO2max (the maximum amount of oxygen your body can use during exercise) and extends time to exhaustion, making it especially attractive in endurance sports like cycling, distance running, and cross-country skiing. It also improves recovery between efforts, since muscles get more oxygen during rest periods. Blood doping through transfusions works on the same principle: adding extra red blood cells to the bloodstream increases oxygen-carrying capacity without the athlete’s body needing to produce them.
Growth Hormone and Body Composition
Human growth hormone (hGH) is produced by the pituitary gland and plays a key role in growth, metabolism, and tissue repair. Athletes misuse synthetic hGH primarily for its ability to shift body composition: it increases lean body mass and decreases body fat, redistributing fat from the midsection to more peripheral areas. It also increases total body water, which can make muscles appear fuller.
Beyond body composition, hGH appeals to athletes because of its effects on carbohydrate and fat metabolism. The body becomes better at burning fat for fuel while preserving muscle glycogen. Clinical studies on hGH treatment over four to six months showed favorable effects on exercise capacity and overall physical function. However, the actual performance gains from hGH alone are debated, and many athletes combine it with anabolic steroids to amplify the effects of both.
Stimulants and Mental Performance
Stimulants target the central nervous system to reduce fatigue, increase alertness, and sharpen reaction time. They’re particularly useful in sports that demand quick reflexes or sustained concentration, though they also provide a physical edge by raising heart rate and aggressiveness.
Amphetamines are among the most potent, improving reaction time in fatigued athletes and increasing both muscular strength and endurance. Cocaine produces short bursts of euphoria, mental clarity, and reduced fatigue, though its effects fade quickly. Ephedrine, often found in dietary supplements marketed for energy and fat loss, has been shown to increase time to exhaustion on cycling tests, especially when combined with caffeine. Caffeine itself, while not currently banned, produces mild stimulant effects that reduce fatigue and improve concentration. It’s one of the most widely used ergogenic aids in sport.
Masking Agents and Weight Manipulation
Diuretics occupy a unique spot on the banned list. They don’t directly improve performance, but they serve two purposes that make them valuable to cheating athletes. First, they cause rapid water loss, which can help competitors in boxing, wrestling, weightlifting, and other weight-class sports drop several pounds in a short window to qualify for a lower division.
Second, and more critically, diuretics act as masking agents. By dramatically increasing urine volume, they dilute the concentration of other banned substances and their metabolites, making detection by anti-doping labs far more difficult. Some diuretics also alter the pH of urine, which further disrupts the normal excretion patterns of other drugs. This dual utility is why WADA banned diuretics in 1988, both in and out of competition, and why they’re grouped alongside other masking agents in class S5 of the Prohibited List.
Cardiovascular Risks of PED Use
The health consequences of PEDs vary by substance, but the cardiovascular damage from anabolic steroids is among the most serious and well-documented. A study published in Circulation, the journal of the American Heart Association, compared 1,189 steroid users against nearly 60,000 controls and found stark differences.
Steroid users had a threefold increased risk of heart attack, a nearly ninefold higher risk of developing cardiomyopathy (a disease of the heart muscle), and roughly 3.6 times the risk of heart failure. Arrhythmias were 2.3 times more common, with atrial fibrillation and flutter accounting for over half of those cases. The risk of blood clots in the veins was 2.4 times higher, and coronary procedures like stents or bypass surgery were about three times more likely.
The mechanisms behind this damage are layered. Steroids cause high blood pressure and unhealthy cholesterol profiles, which accelerate plaque buildup in arteries. They increase red blood cell production and alter platelet behavior, raising the risk of clot formation. Imaging studies reveal that steroid users develop thickened heart walls and reduced pumping efficiency, changes that persist even after they stop using. These structural changes create the conditions for dangerous heart rhythms and progressive heart failure.
How Athletes Get Caught
Anti-doping testing has evolved well beyond simply checking a single urine sample for banned substances. The most significant advancement is the Athlete Biological Passport (ABP), which tracks an individual athlete’s biological markers over months or years to build a personal baseline.
The ABP has two main modules. The blood module monitors markers like hemoglobin concentration, red blood cell count, and reticulocyte percentage (reticulocytes are immature red blood cells that spike when the body is producing blood cells at an unusual rate). If an athlete’s values suddenly fall outside their established personal range, it raises a red flag for blood doping or EPO use even without detecting the substance itself. The steroidal module, operational since 2014, tracks the ratios of naturally occurring steroids in urine, including testosterone and several of its metabolic byproducts. Unusual shifts in these ratios suggest external steroid use.
This longitudinal approach is powerful because it doesn’t require catching an athlete with a specific substance in their system at a specific moment. Instead, it identifies the biological fingerprints that doping leaves behind.
How Common Is PED Use?
Getting accurate numbers on doping is inherently difficult because athletes have every incentive to hide it. Official test failure rates tend to hover around 1 to 2%, but anonymized surveys paint a different picture. A study of 1,398 U.S. elite athletes subject to WADA-code testing found that 6.5 to 9.2% reported using a prohibited substance or method in the previous 12 months without a therapeutic use exemption. That range depends on how strictly the responses were interpreted, but even the lower estimate is several times higher than what testing alone catches.
Therapeutic Use Exemptions
Athletes with legitimate medical conditions can apply for a Therapeutic Use Exemption (TUE) to use a substance that would otherwise be banned. An athlete with asthma, for example, may need an inhaler containing a prohibited beta-2 agonist. Four conditions must be met: the substance must treat a diagnosed medical condition, it cannot enhance performance beyond restoring normal health, there must be no reasonable permitted alternative, and the need for the substance cannot stem from prior unauthorized drug use.
Applications go through the athlete’s national anti-doping organization or international federation, and a medical committee must approve them within 21 days. If granted, the exemption specifies exact dosages, frequency, and duration. TUEs are a necessary part of the system, but they’ve also drawn scrutiny when high-profile athletes receive exemptions for substances that could plausibly offer a competitive edge.