Content medically reviewed and refreshed 20th July 2026
Androgenic-anabolic steroids (AAS) have been used to enhance athletic performance since the 1940s, but many of the health risks of steroid use have only become clear more recently. Anabolic steroids affect the whole body, not just muscle — so alongside their effect on muscle growth, they can also affect other organs and systems. That's one reason regular health screening and blood testing matters for anyone who has used or is considering these drugs.
How do anabolic steroids work?
Anabolic steroids are synthetic derivatives of testosterone, which is responsible for both muscle development (the "anabolic" effect) and the development of male sexual characteristics (the "androgenic" effect).
Anabolic steroids act on the body in several ways:
- Weight training creates tiny micro-tears in muscle fibres. Testosterone stimulates the creation of new, bigger muscle fibres in response — and anabolic steroids exaggerate this reaction due to the high doses typically involved.
- They stimulate growth hormone (GH) production, which in turn raises IGF-1 — a hormone with growth-promoting effects on almost every cell in the body, especially skeletal muscle, cartilage and bone.
- Intense exercise releases cortisol, which breaks down muscle tissue. Anabolic steroids inhibit this breakdown, adding to the overall anabolic effect.
- There is evidence anabolic steroids may increase oxygen uptake and cardiac output.
- They may also affect athletic performance indirectly, by increasing aggression.
Unintended physical consequences
A common misconception is that because anabolic steroids are a synthetic version of a hormone the body already makes, they must be safe to use. In reality, the body tightly regulates testosterone within a narrow range — too high or too low a level can cause harm — and the doses typically used for performance or physique purposes are far higher than what circulates naturally. This can lead to a range of physical side effects, with shrunken testicles and male breast growth among the most well-known. Excess androgens can also contribute to male-pattern baldness, treatment-resistant acne and changes in libido.
Chronic use causes the body to reduce its own natural testosterone production. This can lead to testicular shrinkage and, in some cases, a lasting reduction in the body's own hormone output. Testosterone also converts into oestrogen, which plays a role in libido, erectile function and sperm production — so excess testosterone can push oestrogen to abnormal levels, contributing to gynecomastia (breast tissue enlargement in men). These effects can be permanent.
What lies beneath
Beyond the more visible effects, anabolic steroid use carries risks that aren't always obvious but can be serious. Blood testing can help detect some of these changes — but it's important to know that many harmful effects may not show up in bloodwork until damage is already advanced, and some conditions become harder to treat the longer steroid use continues.
Here are 7 ways anabolic steroids can affect your health without you necessarily noticing:
1. Cardiovascular disease Studies in athletes and bodybuilders show anabolic steroids can raise LDL ("bad") cholesterol and lower HDL ("good") cholesterol, increasing the risk of atherosclerosis and heart disease — including angina, heart attack and sudden cardiac death. Steroid use is also linked to elevated C-reactive protein (CRP), a marker of inflammation associated with cardiovascular risk. Chronic use can also thicken the heart's main pumping chamber (left ventricular hypertrophy), reducing its ability to pump effectively over time, and has been associated with high blood pressure in some users. Large cohort data has also linked anabolic steroid use to a markedly increased risk of cardiomyopathy and venous thromboembolism (blood clots in the veins) — two of the more serious cardiovascular consequences now recognised in the literature.
2. Liver toxicity Most steroid metabolism happens in the liver, making it particularly vulnerable to damage — even in people without pre-existing liver conditions. ALT and AST are the two liver enzymes most commonly elevated with anabolic steroid use, alongside ALP and GGT. Significant liver damage can occur even while these markers still look normal, since they often only rise once damage is well underway.
3. Kidney injury The kidneys filter waste products from the blood. High-protein diets — common among people using anabolic steroids — increase the kidneys' workload, and combined with steroid use this extra strain can contribute to scarring and, in severe cases, kidney failure.
4. Infertility Anabolic steroid use lowers luteinising hormone (LH) and follicle-stimulating hormone (FSH), both needed for sperm production — changes that can begin within 24 hours of starting use and lead to reduced fertility within months. Recovery is variable and depends largely on how long and how heavily someone has used steroids: men who have used AAS for under a year typically recover within about a year of stopping, while those with more prolonged use (a year or more) may experience delayed or incomplete recovery and may benefit from medical treatment to support recovery. Some men also experience impotence, difficulty urinating, or an increased risk factor for prostate issues — which is one reason regular prostate checks matter for long-term users.
5. Impaired glucose tolerance Anabolic steroid use can affect how the body handles blood sugar and has been linked to an increased risk of type 2 diabetes — which in turn raises the risk of kidney damage, heart disease, stroke and other complications. It's also been associated with features of metabolic syndrome more broadly, including insulin resistance, high blood pressure, unhealthy cholesterol levels and increased abdominal fat. Fasting blood glucose and insulin testing — such as our Insulin Resistance Test — can help flag these changes early.
6. Blood disorders Steroid use can raise red blood cell production, haemoglobin and haematocrit, a condition known as erythrocytosis — one of the most commonly reported adverse effects of anabolic steroid use. Thickened blood of this kind increases the risk of dangerous blood clots.
7. Thyroid dysfunction Some studies suggest anabolic steroid use may have an effect on thyroid function, though the evidence here is more limited than for the other risks in this list. Annual thyroid checks are still a sensible part of routine monitoring for anyone using or who has used anabolic steroids.
The importance of blood work
The health consequences of anabolic steroid use — particularly to the heart and liver — can be well advanced by the time physical symptoms appear. The clearest medical advice from any health professional is not to use these substances. For anyone who has used them, or is currently using them, blood testing can help identify some of the changes described above and give you and your doctor a clearer picture to work from. Markers worth discussing with your GP include:
- Cholesterol status — HDL, LDL and triglycerides, key contributors to cardiovascular risk.
- Inflammation markers — CRP and creatine kinase, which offer insight into cardiovascular and muscle health.
- Liver function — ALT, AST, ALP and GGT, to check how your liver is coping.
- Kidney function — waste products, electrolytes, minerals and glucose.
- Full blood count — red blood cells, haematocrit and haemoglobin.
- Hormone profile — testosterone, free testosterone, FSH, LH and oestradiol.
Understanding your own baseline levels — and tracking how they change over time — gives far more useful information than a single test in isolation.
If you're concerned about any of the effects described here, the safest step is speaking with your doctor. Blood testing, such as our Sports Hormone Check (male), can give you and your GP a clearer picture of what's happening in your body. You can also read more about the testosterone:oestradiol ratio and men's health, or explore our full range of athletic performance and recovery testing.
This article is for general educational purposes and does not constitute medical advice. If you have questions about steroid use or your health, please speak with your doctor.
