Creatine
Summary:
Creatine (monohydrate) supplementation, according to the International Society of Sports Nutrition, is the most effective ergogenic (performance enhancing) nutritional supplement currently available to athletes in terms of increasing high-intensity exercise capacity and lean body mass during training. Many forms are available and discussed in the full summary, but have not been shown to exert significant benefits over basic monohydrate supplementation.
Creatine's main action in the body is to store high-energy phosphate groups in the form of phosphocreatine. During periods of stress, phosphocreatine releases this energy to aid the cell's functions. This mechanism of action is what causes creatine to increase strength, but can benefit almost every body system, including the brain, bones, muscles, and liver. Most benefits of creatine occur through this energy mechanism.
Creatine is produced naturally in the body, and it is also found in foods (mostly meats, eggs, and fish; some in dairy).
Creatine supplementation at normal dosages and with adequate hydration has been shown to have no harmful effects in any population tested (More info in full summary under General Safety Profile). The only observed side effects are stomach cramping if consumed with insufficient water, and diarrhea if too much is consumed at once. Controlled usage of creatine with adequate water may actually reduce cramping over the long term.
Assuming Creatine Monohydrate (most frequently used in studies) is the standard by which to compare, no form of creatine has shown to be more powerful or potent. Overall, Creatine Monohydrate is the best 'bang-for-you-buck' form of creatine as the others tend to carry higher prices on the labels. That being said, other forms may have benefits that are not related to the creatine molecule itself but due to solubility. Those with stomach cramping with creatine (which may be due to creatine monohydrate forming an insoluble precipitate in the stomach) should consider a more water-soluble form of creatine.
Dosage:
Most studies use a 'loading protocol' of 0.3g/kg bodyweight for 5-7 days followed by 5g of creatine monohydrate afterwards. For a 200lb individual, this correlates to 27g a day for 5-7 days, followed by a period of time with 5g a day. This ensures quick saturation of cells with creatine phosphate.
Saturation can also be achieved at a slower rate with a constant dose of 3-10g creatine monohydrate for an extended period of time.
Cycling is often used in conjunction with the loading protocol, but is not needed.
All information taken from:
http://examine.com/supplements/Creatine/#summary13-0