Creatine Loading Protocol: 20g/Day for 5-7 Days — What the Research Says

Origins of the Loading Protocol

The creatine loading protocol emerged from early investigations into phosphocreatine metabolism conducted at the Karolinska Institute in Stockholm. Harris et al. (1992) published the foundational study demonstrating that oral creatine monohydrate supplementation could significantly elevate intramuscular total creatine concentrations in human subjects. Their work in Clinical Science showed that ingesting 5 g of creatine monohydrate four to six times daily for two or more days increased total muscle creatine content by approximately 20%, with some subjects achieving increases of up to 30 mmol/kg dry weight.

This finding was remarkable because it demonstrated a dietary intervention capable of meaningfully altering skeletal muscle biochemistry within days rather than weeks. Prior to this work, phosphocreatine levels were considered relatively stable properties of muscle tissue, modifiable only through chronic training adaptations. Harris and colleagues showed that the creatine transporter system was not fully saturated under normal dietary conditions, leaving room for exogenous supplementation to increase intracellular stores.

Building on the Harris data, Hultman et al. (1996) systematically characterized the loading and maintenance phases in a study published in the Journal of Applied Physiology. They confirmed that 20 g/day (divided into four equal 5 g doses) for five to six days reliably elevated muscle total creatine from a baseline of approximately 120 mmol/kg dry weight to approximately 140-155 mmol/kg dry weight. Subjects with lower initial creatine concentrations (such as vegetarians) showed the greatest absolute increases, while those with already-elevated baseline levels experienced more modest gains.

The Standard Protocol: 4 x 5 g Per Day

The conventional loading protocol involves consuming 20 g of creatine monohydrate daily, split into four equal doses of 5 g each, over a period of five to seven days. The rationale for dose fractionation is pharmacokinetic: a single 5 g dose produces a plasma creatine peak approximately 60-90 minutes after ingestion, and renal clearance begins to increase substantially as plasma levels rise. Splitting the dose maintains elevated plasma creatine for more hours of the day, maximizing the time window during which muscle uptake can occur.

Muscle creatine uptake follows saturation kinetics. The sodium- and chloride-dependent creatine transporter (CRT, encoded by the SLC6A8 gene) has a finite transport capacity. During loading, uptake is highest in the first two days when the gradient between plasma and intracellular creatine is greatest. By days four and five, uptake rates decline as intramuscular stores approach their ceiling. Most individuals achieve near-maximal saturation within five days. Extending loading to seven days provides a small additional increment for non-responders or individuals with higher muscle mass.

The total creatine pool in a 70 kg individual is approximately 120-140 g, with roughly 95% residing in skeletal muscle. Daily turnover (degradation of creatine and phosphocreatine to creatinine) amounts to approximately 1.7-2.0% of the total pool, or roughly 2 g per day. Loading rapidly fills the pool beyond what diet alone (typically contributing 1-2 g/day from meat and fish) and endogenous synthesis (approximately 1 g/day from the liver and kidneys) can maintain.

Muscle Biopsy Evidence for Saturation

The gold standard for verifying creatine loading efficacy is muscle biopsy, typically obtained from the vastus lateralis. Hultman et al. (1996) obtained biopsies before and after the loading phase and documented total creatine increases averaging 20-25 mmol/kg dry weight. Importantly, they observed substantial inter-individual variation. Approximately 20-30% of subjects were classified as "non-responders," showing increases of less than 10 mmol/kg dry weight. These individuals tended to have higher baseline creatine levels, suggesting their muscle stores were already near the physiological ceiling of approximately 155-160 mmol/kg dry weight.

The proportion of the elevated creatine that exists as phosphocreatine (PCr) versus free creatine (Cr) is physiologically relevant. After loading, both fractions increase, but the PCr/Cr ratio tends to shift modestly toward free creatine in resting muscle. During exercise, the expanded PCr pool enables greater ATP resynthesis during high-intensity efforts, which is the primary ergogenic mechanism.

Casey et al. (1996) corroborated these findings using phosphorus-31 magnetic resonance spectroscopy (31P-MRS) as a non-invasive alternative to biopsy. Their data confirmed that muscle PCr concentrations increased significantly after five days of loading at 20 g/day, and that this increase correlated with improved performance in repeated maximal voluntary contractions. The 31P-MRS approach also demonstrated faster PCr resynthesis between bouts of exercise, indicating enhanced recovery capacity at the metabolic level.

Saturation Timeline

The temporal dynamics of muscle creatine accumulation during loading are well characterized. Approximately 30-40% of the total loading increment occurs in the first two days, with the majority of remaining uptake distributed across days three through five. By day five, plasma creatine levels during the post-dose window are largely excreted renally rather than taken up by muscle, indicating that the intracellular compartment is approaching capacity.

Urinary creatine excretion provides an indirect marker of loading completeness. During the first two days of loading, urinary creatine excretion is relatively low (indicating efficient muscle uptake). By days four and five, urinary excretion increases substantially, sometimes reaching 40-60% of the ingested dose. This shift from retention to excretion signals that the muscle compartment is nearing saturation and additional loading provides diminishing returns.

After loading, the transition to a maintenance dose of 3-5 g/day is sufficient to sustain elevated stores. Hultman et al. (1996) showed that without maintenance dosing, creatine levels returned to baseline over approximately 28-30 days, consistent with the known daily turnover rate of approximately 2 g/day and the roughly 20-40 g of additional creatine stored during loading.

Gastrointestinal Tolerance

The most commonly reported side effect of the loading phase is gastrointestinal discomfort, including bloating, nausea, diarrhea, and stomach cramping. These symptoms are dose-dependent and related to the osmotic effects of unabsorbed creatine in the intestinal lumen. When 5 g of creatine monohydrate is dissolved in water, the resulting solution draws fluid into the gut via osmosis. Taking multiple large doses in a single day increases the likelihood of GI disturbance.

Ostojic and Ahmetovic (2008) reported that dividing the 20 g daily dose into smaller portions (e.g., four doses of 5 g or even ten doses of 2 g) reduced GI symptoms without compromising total muscle uptake. The practical recommendation from the literature is to consume each 5 g dose with at least 250-300 mL of water, taken with meals when possible, and to space doses at least three to four hours apart.

It is worth noting that GI symptoms during loading are generally mild, self-limiting, and affect a minority of users. In large-scale reviews of creatine supplementation trials, including the comprehensive 2017 position stand by the International Society of Sports Nutrition, the incidence of clinically significant GI side effects during loading is low when dosing guidelines are followed.

Who Benefits from Loading

Loading is most advantageous when rapid saturation is desired. Athletes facing an imminent competition, individuals beginning a peaking block in training, or anyone who wants to begin experiencing the ergogenic effects of creatine within the first week of supplementation may prefer the loading approach. The alternative, taking 3-5 g/day without loading, achieves the same saturation endpoint but requires approximately 28 days (as demonstrated by Hultman et al., 1996).

Vegetarians and vegans tend to have lower baseline intramuscular creatine due to the absence of dietary creatine from meat and fish. This population generally shows the most pronounced response to loading, with larger absolute increases in muscle creatine and often more noticeable performance improvements. Burke et al. (2003) specifically examined vegetarians and found significantly greater lean mass and muscular performance gains compared to omnivores following the same loading protocol.

Conversely, loading is not strictly necessary. As detailed in the companion article on skipping the loading phase, daily low-dose supplementation achieves equivalent saturation given sufficient time. The choice between loading and gradual accumulation is ultimately one of convenience and tolerance rather than of efficacy at steady state.

Who Might Skip Loading

Individuals with sensitive gastrointestinal systems, those who dislike taking large doses of any supplement, and anyone without time-sensitive performance goals can reasonably opt out of loading. The endpoint is the same: saturated muscle creatine stores maintained by a daily dose of 3-5 g. The only difference is the time required to reach that endpoint.

Additionally, individuals who are already consuming substantial dietary creatine (e.g., those eating over 1 kg of red meat per day, which would provide approximately 4-5 g of creatine) may have partially elevated baseline stores, reducing the relative benefit of a rapid loading phase. For these individuals, a maintenance dose alone may be sufficient from the outset, though this scenario is uncommon in practice.

Practical Recommendations

Based on the totality of published evidence, the following protocol represents the standard loading approach:

1. Consume 5 g of creatine monohydrate four times per day (total: 20 g/day) for five to seven days.
2. Dissolve each dose in at least 250-300 mL of water or other fluid.
3. Space doses at least three to four hours apart (e.g., breakfast, lunch, afternoon, dinner).
4. Taking doses with meals may improve GI tolerance and, per Green et al. (1996), the insulin response from carbohydrate-containing meals may modestly enhance muscle creatine uptake.
5. After five to seven days, transition to a maintenance dose of 3-5 g/day.

There is no evidence supporting doses higher than 20 g/day for loading. Excess creatine beyond what the transporter system can handle is simply excreted in the urine, providing no additional benefit while increasing cost and GI burden.

Summary

The loading protocol is a well-validated method for rapidly elevating intramuscular creatine stores to near their physiological maximum. Five days of 20 g/day (4 x 5 g) produces consistent increases of 20-25 mmol/kg dry weight in most individuals, as confirmed by muscle biopsy and MRS data. GI side effects are manageable with proper dose fractionation. Loading is most appropriate when rapid saturation is desired, particularly for vegetarians and athletes with near-term competitive demands. The alternative of chronic low-dose supplementation (3-5 g/day) reaches the same saturation point in approximately four weeks.

Bibliography

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2. Hultman E, Soderlund K, Timmons JA, Cederblad G, Greenhaff PL. Muscle creatine loading in men. Journal of Applied Physiology. 1996;81(1):232-237. doi:10.1152/jappl.1996.81.1.232. PMID: 8828669.
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6. Ostojic SM, Ahmetovic Z. Gastrointestinal distress after creatine supplementation in athletes: are side effects dose dependent? Research in Sports Medicine. 2008;16(1):15-22. doi:10.1080/15438620701693280. PMID: 18373285.
7. Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition. 2017;14:18. doi:10.1186/s12970-017-0173-z. PMID: 28615996.