The Food and Drug Administration (FDA) on Tuesday asked the makers of testosterone boosting products, which are used by millions of Americans, to change labels for the drugs.

According to recent FDA orders the manufacturers of the testosterone drugs will have mention on their product's label a warming that the drugs could increase the risk of heart attacks and strokes in patients taking the medications.

The FDA's notification also asks the manufacturers that labels of such drugs need to clarify that the prescription hormone is meant for use by men whose low testosterone levels situation have occurred by certain medical conditions, and not by normal aging.

As per health experts, some genetic disorders and conditions affecting the testicles, pituitary gland and brain can also lead to low testosterone levels.

Despite several research evidence showing that testosterone boosting drugs are associated with high risk of heart attacks and strokes, almost 3% of American men above the age of 40 are boosting their testosterone levels with a prescription supplement.

Vigorous advertising campaigns led to a five times rise in the testosterone prescriptions between 2000 and 2011, netting the makers of the products $1.6 billion annually.

The FDA on Tuesday said, "The FDA has become aware that testosterone is being used extensively in attempts to relieve symptoms in men who have low testosterone for no apparent reason other than aging. The benefits and safety of this use have not been established".

The risks to those taking testosterone are not fully understood, and researches that have given worrisome results have had methodological problems. Several trails have failed to find the risk of heart attacks and strokes.

The FDA has estimated that 1.5 million men were taking a testosterone supplement in 2013, nearly double the 850,000 men who were taking it in 2010.