Here's a shorter version of the articel by John for anyone who is interested
"Researchers initially found that 20 grams per day of creatine, taken for five days, successfully raised muscle creatine content by 30-45 percent. The same protocol—20 grams per day, then maintenance of supraphysiological concentration with 2-3 grams daily after that—has been used since 1996[43] with little to no deviation in the research.
Consider the fact that a 150 pound male (70 kilograms) will burn through about two grams of creatine naturally every day[44]. Since 95 percent of creatine exists within muscle tissue, the average resistance-trained athlete would require greater amounts of creatine just to maintain normal cellular levels.
The two-grams-per-day maintenance level is the current recommendation by the American College of Sports Medicine’s expert panel on creatine[45]. After using more advanced methods of determining intracellular creatine levels in 2003, however, researchers found that after two weeks of using the standard protocol, intracellular creatine levels returned to baseline[46].
The 20 grams-per-day mark was little more than an arbitrary choice by early investigators, and for some reason, it stuck. Even researchers using formulas accounting for bodyweight and body mass still assumed that a 150 pound man should take 20 grams of creatine per day. Nobody tested this assumption.
This can’t possibly be the optimal dosing schedule for everyone. Humans carry about two grams of creatine per kilogram of lean muscle mass (one gram per pound). The maximum we can put into muscles is about 3g/kg (1.4g/lb)[47]. To hit this level, a 150 pound male would need about 25 grams of creatine supplementation.
To increase the amount of creatine we carry to a level above the baseline (1g/lb), we need at least two grams per day for maintenance, plus 0.4g for every lean pound of muscle. For a 200 pound male carrying 60 pounds of lean muscle, a reasonable calculation would be:
(0.4g/lb * 60 lbs)/0.95 + 2g ≈ 27.3g
My hypothesis is that this would be the minimum amount of creatine needed, daily, to maintain maximum intracellular levels—with the division by 0.95 taking into account the amount of creatine absorbed by the rest of the tissue in the body. There may be a better way to estimate the minimum daily dose, but the data for this doesn’t yet exist.
This alleviates the need for a loading period. If you’re fairly lean, this leads to a simple formula:
POUNDS: Bodyweight * 0.15 = grams of creatine monohydrate to ingest
KILOGRAMS: Body mass * 0.3 = grams of creatine monohydrate to ingest
Although these formulas would appear to overestimate needs, bear in mind that one gram of creatine monohydrate is only 88 percent creatine. The overage takes this into account."