Robbie Williams regularly injects self with testosterone

Robbie Williams said the doctor told him he had the testosterone of a 100-year-old man which clarified why he needed to inject himself with the hormone. Photo / Supplied

Robbie Williams injects himself with testosterone twice a week.

The 37-year-old Take That singer thought getting a boost of Human Growth Hormone (HGH) would help fight his feelings of lethargy and make him healthier but was told by medical experts his problems stemmed from a lack of the hormone - which boosts a man's sex drive - and says the supplementary injections have changed his life.

He told Britain's Esquire magazine: "I went to the doctor to get some Human Growth Hormone (HGH).

"It's what all the old fellas are on out there in Los Angeles that's making them look 40 instead of 60.

"It's improving their health, their memory, their hair, skin.

The hormones may have side effects that could be detrimental but Robbie said he weighed the options up.

"Could give you cancer. I weighed that up. Thought I'd have it anyway."

Robbie said he went to see a Hollywood doctor and had his blood tested, the doctor's revelation made everything clear to him.

The doctor said: "'You've got the testosterone of a 100-year-old man.'"

"And then everything made sense. It was kind of an epiphany that day,' Robbie said.

Accordingly his relationship with Ayda Field also seems to be working out.

Robbie married the US actress last August and insisted he will always remain faithful to her.

When asked if he could ever see himself cheating on Ayda, he replied: "Actually, no, because I don't want to break Ayda's heart. That's the last thing I want to do. I met Ayda, I fell in love, that's what happened."

Although, the Angels hitmaker did speak up on his belief that people naturally want to cheat and branded marriage "made-up bull".

He said: "The rules aren't set up right. Because people are f***ing outside of their marriages, outside of their relationships. I think that means we're built to f***.

"And marriage, that whole institution, is made-up bull."

- BANG! Showbiz