Creatine is widely considered safe when taken in recommended dosages by healthy individuals. Extensive research supports its efficacy and safety, even during prolonged use.

Here are some key points based on authoritative sources:

1. General Safety: The International Society of Sports Nutrition (ISSN) states that creatine monohydrate is safe and effective for increasing high-intensity exercise capacity and lean body mass. It does not have detrimental effects on otherwise healthy individuals[^1^][^2^].

2. Long-Term Use: Studies have shown that long-term creatine supplementation (up to 21 months) does not adversely affect clinical markers of health. This includes a comprehensive panel of serum, blood, and urine markers assessed in athletes[^3^][^4^].

3. Anecdotal Side Effects: While there are anecdotal reports of muscle cramps, gastrointestinal complaints, and kidney issues, these are not commonly supported by scientific evidence and may not be directly linked to creatine itself[^5^].

4. Specific Populations: For people with pre-existing kidney conditions or risk factors for renal dysfunction (e.g., diabetes, hypertension), high-dose creatine supplementation is not recommended without medical supervision. However, in healthy subjects, creatine does not significantly impact kidney function[^6^].

5. Cognitive Benefits: Beyond its physical performance benefits, creatine supplementation may also offer cognitive benefits and support in traumatic brain injury cases[^7^].

In summary, creatine is generally safe for healthy individuals when taken as recommended. However, if you have pre-existing kidney issues or other health conditions, consult with a healthcare provider before starting creatine supplementation.