Hitler was administered a cocktail of drugs including cocaine and ground bulls' testicles, fuelling his ranting paranoia, according to a new documentary.

A collection of medical reports commissioned by the US military has just been released and includes interviews with six doctors who treated the Nazi dictator. They are explored in a new documentary by National Geographic TV, called Nazi Underworld - Hitler's Drug Use Revealed.

According to the 47-page document, Hitler suffered from stomach cramps and appalling flatulence.

When morbidly obese physician Doctor Theodor Morell prescribed live bacteria, the ailment eased, and Hitler appointed Morell as his personal physician.

Dr Morell, who was soon nicknamed 'The Reichsmaster of the Injections', also gave Hitler powdered cocaine to "clear his sinuses and soothe his throat" and administered the Fuhrer with eye drops containing 10% cocaine.

When he began to crave the drug, the dose was lowered.

According to the documentary, Hitler's inner circle began to suspect that Morell was a fraud, hired by the Allies to destabilise Hitler's mental health and dubbed him a 'quack', 'phony' and 'charlatan'.

Psychiatrist Professor Nassir Ghaemi argues that the drug use may explain Hitler's increasingly erratic behaviour as the war progressed and may have exacerbated Hitler's manic depression.

"It's not whether Hitler was an amphetamine addict or not - it's that Hitler had bipolar disorder and amphetamines made it worse," he said.

"That would explain a lot why Hitler changed in the late 1930s and the 1940s," said Professor Ghaemi.

Theodor Morell, Hitler's physician
Theodor Morell, Adolf Hitler's personal physician (holocaustresearchproject.org) holocaustresearchproject.org

The report also states that Morell injected Hitler with extracts from the prostate glands or ground testicles of young bulls, to boost his nearly non-existent libido ahead of a night with Eva Braun, his lover, who was 23 years his junior.

"Morell gave Hitler a preparation called Testoviron, a kind of testosterone preparation, usually before Hitler was going to spend a night with Eva Braun," Cambridge University historian Richard Evans said.

"Eva Braun was young and much fitter. Hitler was much older, he was lazy, he didn't take much exercise and I'm sure he asked Doctor Morell to help him out before he went to bed with Braun."

Evans describes a meeting between Hitler and Italian fascist leader Benito Mussolini, at which Hitler appeared to be high on drugs.

"We can be pretty sure Morell gave some tablets to Hitler when he went to see Mussolini because of all the descriptions of him in that meeting," said Evans.

"He's just hyperactive, completely hyper in every way, talking, gabbling, clearly on speed."

According to the documents, Morell's medicine cabinet was found to contain concoctions based on rat poison and an oil used to clean guns.

He confessed to administering opiates, morphine, barbiturates and amphetamines when he was captured by the Allies and accused of criminal negligence

However, experts have warned that the evidence could be used by Holocaust deniers and Neo-Nazis to argue that Hitler was not fully to blame for the atrocities and mass murder committed by the Nazis.

"Just 48 hours before his death Hitler dictated his will, as lucid and alert as ever. His mental capabilities were normal," Hans-Joachim Neumann, author of Was Hitler Ill?, said.

"The Jews were not wiped out because Hitler was ill, but because most Germans followed his decisions. Hitler always knew what he was doing."