More adults and even boys are experiencing a diminished sexual desire, or some kind of erectile dysfunction  

What they'd do about it?
The first thing is: don't panic.

Sexual desire, or sex drive, can go up and down, and most of the time is totally normal.
Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteristics such as increased muscle and bone mass, and the growth of body hair.  Higher levels of testosterone helps boost overall sexual drive or desire for sexual activity.

Many factors are responsible for sex drive or libido, and trying to "fix" something which is natural may only add trouble and disappointment.
The modern culture of "a pill will save me" may do more harm than good.

So, my first advice would be to look at your stress level because sex hormones are regulated in the brain by a master gland called Pituitary gland.
Most of our stress response come from our unconscious mind, so you may not even be aware of it.

When the libido is low desire follows because they're the same thing, but while desire is selective, love is not.

This means that we can still love our partner even when our libido is low.
That's right, an act of love is not necessarily sexual.
So, you don't need to take viagra or other medications, because there is nothing to cure.
Just don't create a disease where there is none.

Instead of reacting to the loss of desire, we could try to use it as an opportunity to improve, to detach ourselves from the person we imagine to be.
That way we transform a threat into a an opportunity to be free from our own worries and fears, which are mentally created.

The practice of human values is simple and effective to clean up our mind, and to move forwards to the inner journey of peace and love. [2]
Sleep disorders, junk food, and poor lifestyle also contribute to the decline of sex drive.
Aging is another factor that reduces the production of testosterone in your testes.

Shall I get testosterone supplements?
I'd suggest to talk with your doctor, but bear in mind that testosterone produced in your testes is not the same as testosterone in pills. If you get testosterone boosters you may in fact reduce the production of natural testosterone even further.

In fact, testosterone therapy might cause more problems than they solve. Studies have suggested a connection between supplements and heart problems. [1]
Testicular shrinkage with a diminished level of natural testosterone is another side effect of testosterone therapy. Pills may artificially increase your blood level of testosterone which in turn will signal the Pituitary to reduce it. As a result you may experience Decreased sperm count, and Infertility. [1]

Other side effects include High blood pressure and insomnia.

Nutrition
Onions and garlic are your allies in the kitchen and in the bedroom. They may help you make more and better sperm. Both help raising levels of testosterone, and both have high levels of natural plant chemical called flavonoids, which may safeguard your li'l swimmers against damage.
Magnesium may help with brain functions that reduce stress and anxiety. Green leaves like Spinach are packed with magnesium . Almonds, cashews, and peanuts are also good sources.
Fresh fruit's may lower levels of stress hormones, such as cortisol, which helps raise levels of sex hormones including testosterone. And it can lower your blood pressure and put you in a better mood!


[1] https://www.healthline.com/health/low-testosterone/do-testosterone-supplements-work#supplements
[2] https://www.fempton.com/human-values