Creatine and Dehydration: The Myth That Won't Die

The claim that creatine causes dehydration has persisted since the supplement gained popularity in the 1990s. Athletic trainers, coaches, and sports medicine professionals have repeated it for decades, sometimes discouraging creatine use among athletes training in hot environments. The reasoning seems intuitive: creatine draws water into muscle cells, therefore it must deplete water from everywhere else, leading to dehydration. The reasoning is intuitive. It is also wrong.

Controlled studies examining hydration status in creatine users have consistently failed to confirm this hypothesis. Several have found the opposite: creatine supplementation may actually improve hydration status and thermoregulatory capacity during exercise in the heat.

The Theoretical Basis for the Concern

Creatine is an osmolyte. When intramuscular creatine concentrations increase through supplementation, water follows through osmosis. This is why creatine loading typically produces a weight gain of 1-3 kg, most of which is water retained within muscle tissue. The initial concern was that this intracellular water retention would come at the expense of extracellular fluid volume, effectively dehydrating the plasma, interstitial fluid, and other compartments.

This concern was plausible but untested when it first emerged. It assumed that the body's fluid regulatory mechanisms would not compensate for the shift in water distribution. The body, however, possesses sophisticated systems for maintaining fluid balance, including aldosterone-mediated sodium and water retention, antidiuretic hormone (vasopressin) signaling, and thirst mechanisms. The question was always empirical: does creatine-induced intracellular water retention actually compromise overall hydration?

The Lopez et al. Systematic Review

The most comprehensive assessment of this question was published by Lopez et al. (2009) in the Journal of Athletic Training. This systematic review with meta-analysis examined all available controlled studies that measured hydration status, thermoregulation, or exercise heat tolerance in creatine users. The review included studies conducted in both temperate and hot environments.

Their conclusions were unequivocal. Creatine supplementation did not reduce total body water as a proportion of body mass. It did not impair thermoregulatory responses during exercise in the heat. It did not increase the incidence of heat-related illness. In fact, some evidence suggested that creatine users had improved thermoregulation, possibly because the increased total body water provided a larger heat sink.

Lopez et al. specifically noted that the available evidence did not support the recommendation to avoid creatine in hot environments. The widespread prohibition of creatine use during preseason football training (common in some college programs at the time) was based on anecdote rather than evidence.

The Dalbo et al. Review

Dalbo et al. (2008) published a review in the Journal of the International Society of Sports Nutrition that reached similar conclusions. They examined the evidence regarding creatine supplementation and exercise in heat, specifically addressing claims about dehydration and heat illness risk. Their analysis found no controlled evidence supporting increased dehydration risk with creatine use.

Dalbo et al. made an additional point that is often overlooked: creatine increases total body water. The water drawn into muscle cells does not vanish from the body. Total body water increases during creatine loading, meaning the body has more water available overall, not less. The redistribution of water toward intracellular compartments does not deplete extracellular fluid to dangerous levels because the total pool expands.

Controlled Exercise Studies

Several individual studies provide direct evidence against the dehydration hypothesis:

Kern et al. (2001) studied Division I football players during two-a-day preseason practices in hot conditions. Creatine users did not experience greater dehydration, as measured by changes in body mass and urine specific gravity, compared to non-users. Heat illness incidence was not elevated in the creatine group.

Volek et al. (2001) examined thermoregulatory responses during prolonged exercise in the heat. Creatine-supplemented subjects showed no impairment of core temperature regulation. Their sweat rates, cardiovascular responses, and perceived exertion were comparable to controls.

Powers et al. (2003) conducted a controlled study of creatine supplementation during exercise in hot environments. They found that creatine did not adversely affect hydration status, body temperature, or plasma volume during exercise-heat stress. Creatine-supplemented subjects maintained similar fluid balance as placebo subjects.

Watson et al. (2006) examined the effects of creatine on exercise performance and thermoregulation in dehydrated subjects. Even under conditions of deliberate fluid restriction, creatine supplementation did not worsen dehydration-related decrements in performance or thermoregulation.

Total Body Water: The Missing Piece

The key physiological fact that undermines the dehydration myth is that creatine supplementation increases total body water. This has been measured directly using bioelectrical impedance analysis, deuterium oxide dilution, and other validated hydration assessment methods.

During a standard creatine loading phase, total body water increases by approximately 0.5-1.0 liters. This water is distributed primarily to intracellular compartments (particularly skeletal muscle), but the extracellular compartment is not depleted in the process. The body upregulates fluid intake (through increased thirst) and fluid retention (through hormonal mechanisms) to accommodate the new intracellular demand.

This increase in total body water is, if anything, protective against dehydration. An athlete with greater total body water has a larger fluid reserve to draw upon during exercise-induced sweating. This may explain the findings of some studies suggesting improved thermoregulation in creatine users.

Why the Myth Persists

Several factors contribute to the durability of the dehydration myth. First, it is intuitively appealing. The mental model of creatine "sucking water" into muscles at the expense of other tissues is easy to visualize and remember, even though it oversimplifies the body's fluid dynamics.

Second, early anecdotal reports from athletes who experienced cramping or heat illness while taking creatine were attributed to the supplement without controlled investigation. These reports often involved confounding factors: inadequate fluid intake, intense training in extreme heat, rapid weight cutting, and other risk factors that independently cause dehydration and heat illness.

Third, regulatory and institutional momentum has preserved the myth. Once athletic training departments and sports organizations adopted precautionary guidelines against creatine use in hot weather, those guidelines became self-perpetuating. Reversing institutional policy based on updated evidence is slow, particularly when the original policy errs on the side of caution.

Practical Implications

The evidence supports the following conclusions for athletes and active individuals:

Creatine supplementation does not require additional fluid intake beyond normal hydration practices. Standard recommendations to drink adequate water based on body weight, activity level, and environmental conditions remain appropriate. There is no need for special hydration protocols solely because of creatine use.

Creatine can be used safely during training in hot environments. The evidence does not support restricting creatine use during summer training, preseason camps, or competition in warm climates.

If an athlete experiences dehydration or heat illness while taking creatine, the cause should be investigated through the same clinical lens applied to any athlete: Was fluid intake adequate? Was the training load appropriate for the conditions? Were acclimatization protocols followed? Attributing the event to creatine without investigating these factors is not evidence-based practice.