The difference between weight loss and death is only a small concentration change in dinitrophenol, making the drug dangerous.
Side Effects are:
Overheating - There is no upper limit to DNP's body temperature increase, meaning that one may literally "cook from the inside" if they take too much.
Carcinogenesis - Phenols in general are reputed to be carcinogenic. Although 2,4-dinitrophenol has never been implicated in a cancer diagnosis, some are nonetheless concerned, and understandably so. In addition to the inherent carcinogenic potential caused by its status as a phenol, production of free radicals and the release of various compounds stored in adipose tissue stores during DNP's rapid oxidation of fat may also potentially be harmful.
Discomfort and sweating - This is the single most noticeable effect of DNP use, both by the user and those around him. Even in the winter, while indoors at ambient temperatures, one may expect his shirt to be completely soaked through with sweat.
Insomnia - Second in frequency to sweating and discomfort is insomnia; this may be at least partially attributed to discomfort.
Yellow bodily fluids - Some don't notice this, but others find that all of their bodily fluids take on a yellowish appearance. Urine is a darker yellow, and even semen may be affected. According to current knowledge, this is not known to be harmful in and of itself.
Muscle Soreness - This is yet another thing that may be minimized via cerebral function. Low levels of ATP are a cause of muscle soreness in and of itself; the additional factor of encumbered recovery mechanisms make extreme soreness quite possible.DNP is an uncoupling agent that inhibits the flow of electrons and the pumping of H+ ions for ATP synthesis.If electron transport does not produce ATP, then much more sugar must be metabolized for energy needs.
Allergic Reactions – These are highly individualized but may be summarily discussed. Various reactions are common with DNP use, and approximately 10% of users will be extremely allergic to it. Allergic reactions can include hives, blisters, and/or inexplicable rashes.
Carbohydrate Cravings - As with most diets, willpower is sometimes the single most important factor.