Normally, synthetic pharmaceutical drugs cannot be used in dietary supplements, but it has been claimed that methylhexanamine is natural and can be found in the oil extracted from geraniums. In the United States the FDA generally does not have the authority to regulate natural chemical compounds this way.
There is at least one scientific report suggesting that geranium oil does indeed contain trace amounts of methylhexanamine. A more recent and more thorough study that used multiple research labs and multiple plants types from multiple sources failed to find even a trace of methylhexanamine in any sample. Nevertheless, for many years, the FDA did not intervene because it was potentially natural.
So if a supplement claims to contain methylhexanamine because it uses geranium oil, then the consumer is getting only uselessly small amounts of it, if any. And if a “natural” supplement does contain a pharmacologically useful amount, then it is surely adulterated with synthetic material produced in a laboratory.
In recent years, potential hazards associated with consumption of methylhexanamine-containing supplements have concerned the FDA enough for them to take action. Elevated blood pressure, cardiovascular problems, shortness of breath, tightening of the chest, heart attacks, and even death have been reported. So the FDA does not currently permit supplements that contain methylhexanamine to be sold in the United States.
Chemistry and Life 