Athletes take steroids in large amounts, and often take more
than one type of steroid at the same time. This is called
"stacking," or "stacking the pyramid."(1-3)

Athletes do not usually take high doses of steroids all the
time. Instead they take large amounts of steroids for 4 to 18
weeks, then stop taking them for 1 to 12 months. This is called
"cycling."(2,4,5) Combinations of stacking and
cycling vary greatly from one steroid abuser to the next. Methods
of use are passed from one person to another by word of mouth
instead of being based on scientific experiments. The doses taken
by younger athletes today may be as much as 36% higher than the
anabolic steroid doses taken by athletes in past years.(6)
Formal scientific studies are lacking, and no one knows whether
stacking and cycling cause more muscle growth than taking normal
doses of steroids.(5)

Most anabolic steroid abusers purchase these drugs on the
black market. Because there are no controls over this activity,
the identity and purity of the drugs are questionable. Athletes
and others sometimes use veterinary steroids.(5,7)
Since these were developed for use in animals, there have been no
studies in humans to determine the dose or predict side
effects.(5)

Like other black market drugs, bootleg anabolics are being
made in illegal laboratories.(7-9) They look like
the actual drug, but may not have the same active ingredients or
the right strength.(9) For example, methandrostenolone
(Dianabol(R)) was a popular anabolic steroid. After being taken
off the market by its legitimate manufacturers(5,9), it
continues to be sold illicitly. A study recently analyzed three
samples labeled "methandrostenolone." Instead of the steroid on
the label, one contained methyltestosterone, another was caffeine,
and the third had no active ingredients.(9) In addition,
injectable drugs made in illicit laboratories may not be sterile.

With any drug, the higher the dose, the more likely it is that
side effects will appear. This holds true for anabolics as well.
Anabolic abusers sometimes take other drugs to control the side
effects caused by the steroids7) Estrogen blockers are
taken to prevent breast enlargement (look under the question, "What
effects do anabolic steroids have on adults?" to understand why
this happens); Diuretics (fluid pills) are taken to treat fluid
retention; Human Chorionic Gonadotropin is taken to prevent
testicular atrophy; Human Growth Hormone is taken to increase
muscle and body size.(7) Each of these drugs carries side
effects of its own.

You make it sound like most athletes use steroids... :

All national and international level body builders take steroids. Bcoz without them the perfection cant be arrived at all as u see in international body builders. But the use of steroid is most important . Steroids are dangerous only if they are used in excess quantity or prolonged use . A proper use in good guidance and for a small cycle, the results will be very good in terms of muscle growth without any side effects. Arnold, Stallon, loui ferringo all these are steroid built , but still living healthy life even after 65 of age. Thats bcoz they tokk it in proper dosage. Remember even excess protein can damage the kidneys!!!!!!