Creatine vs Vitamin B12
for energy / fatigue
Stronger evidence: tie
Stronger effect: tie
Safety: No notable interactions recorded for either.
For energy / fatigue, the two are evidence-matched; the difference is in effect and safety.
Creatine
grade C low certainty
may reduce mental fatigue, especially under sleep deprivation or stress
3–5 g/day, adults
Vitamin B12
grade C low certainty
corrects fatigue when B12 deficiency is present; no energy benefit in replete people
RDA-to-high oral, adults
sources: PMID:20000106 · PMID:10000010