You're probably taking creatine supplements to increase muscle mass and/or enhance athletic performance. There are several studies that indicate creatine supplementation can increase strength and endurance when dosed in certain ways (loading + maintenance, etc.). However, potential side effects of long-term use of creatine supplements
may include: muscle cramps, stomach cramps, diarrhea, nausea, seizures, and dehydration. There also exists a potential danger of renal toxicity when creatine is taken alone or in combination with certain over-the-counter medications (cimetidine, NSAIDs, etc.).
Interestingly, vegetarians might benefit most from creatine supplementation since they normally have lower levels of creatine than those who eat meat. In
one well-controlled study, vegetarians supplemented with creatine demonstrated enhanced cognitive and memory performance.
Long-term effects of creatine supplementation are unknown.
It has been hypothesized that creatine causes a fluid shift into skeletal muscle cells. There appears to be a fair amount of disagreement in the literature as to whether this actually occurs. To the contrary,
Powers et al. demonstrated that creatine supplementation increases total body water without altering fluid distribution among the body compartments. If this is the case, theoretically speaking, one could argue that creatine supplementation might guard against DCS.
Based on all of this research:
If you are a vegetarian, there might be substantial benefits to creatine supplementation.
If you are a child/young adult, you might
not want to take creatine due to the unknown long-term effects of its use.
If you are an elite athlete, you are probably more concerned with the proven performance enhancement of creatine supplementation than the unknown long-term side effects.
If you are a diver, there is a potential theoretical benefit with respect to DCS (increase of total body water)...but this is mitigated by the potential risk of dehydration (unknown mechanism, perhaps fluid shift from extracellular to intracellular compartment).
It seems to me there are just too many unknowns when it comes to creatine supplementation. Why be a guinea pig?