Creatine (monohydrate)

Athletic baseline (5 g/day chronic, Dylan's current):

• Onset: gradual over 2-4 weeks (faster with loading protocol). Acute single-dose effect is not subjectively perceptible at this level.
• Felt effect: more reps in the tank on the last set, less perceived exertion at submaximal loads, faster between-round recovery during sparring rounds, slightly more bodyweight on the scale (mostly intracellular water, not fat). "Pumps" feel slightly fuller during training.
• Cognitive effect at 5 g/day in a well-rested carnivore: minimal-to-none, per the literature and most user reports. Don't expect a nootropic feel from baseline dosing.

High-dose acute (20 g pre-cognitive-stress, Forsberg protocol):

• Onset: ~3-4 hours post-dose for brain creatine peak per Forsberg 31P-MRS data; cognitive readout emerges in same window.
• Felt effect during sleep deprivation: subjects in Forsberg reported reduced perceived effort on cognitive tasks and improved working memory subjectively, consistent with the objective performance data. Not described as stimulating — more "hold the line" against the cognitive degradation that sleep loss usually produces.
• GI: 20 g is the threshold where GI tolerability becomes a real consideration. Splitting into 4×5 g across 60-90 minutes with hot water and food helps. Some users report bloating or mild diarrhea; resolves within hours.
• This is not a stimulant. It is a metabolic insurance policy that prevents some of the cognitive degradation of sleep loss — it doesn't replace sleep, doesn't stack with caffeine in a particularly synergistic way, and won't create a "wired" feeling.

Loading phase (20 g/day × 5-7 days, then 5 g/day):

• Faster muscle saturation (full pool in 5-7 days vs ~4 weeks at 3-5 g/day maintenance).
• 1-2 kg weight gain in week 1 (intracellular water).
• GI tolerability is the main constraint — split 4×5 g across the day with food. Many users skip loading and just ramp at 5 g/day, accepting the slower saturation. Functional outcome at week 4 is identical.

• Tolerance buildup: none meaningful. Creatine doesn't act on a receptor that downregulates. The pharmacology is structural (intracellular pool size). Once muscle is saturated, taking more doesn't add benefit — but also doesn't blunt it. The body adjusts endogenous synthesis downward when supplementing (~50% reduction in AGAT/GAMT activity), but synthesis rebounds within 3-4 weeks of stopping.
• Recommended cycle: None. No mechanistic reason to cycle for the 5 g/day baseline; user can stay on it indefinitely. The Forsberg 20 g acute protocol is by definition intermittent (1-3× per month, pre-cognitive-stress).
• Reset protocol: N/A. If discontinued, muscle pool drops over ~4-6 weeks to baseline, weight drops by 1-2 kg, performance regresses to pre-supplementation levels. Endogenous synthesis recovers. No withdrawal phenomenon.

Synergistic with

• beta-alanine: Classic combat-sport stack. Beta-alanine elevates muscle carnosine → buffers H+ during glycolytic work (10-90 second efforts); creatine buffers ATP via phosphocreatine (sub-second to ~10 sec efforts). They cover different time domains of energy demand. Hoffman 2006 + Tobias 2013 RCTs show additive performance benefits in repeated-sprint and high-intensity interval work. Dylan stacks both — V4 includes 3 g beta-alanine alongside 5-10 g creatine.
• taurine: Both osmolytes (cellular hydration), both daily-safe, no documented antagonism. Convergent on cellular volume + cardiac function. Common combat-sport pairing.
• caffeine: See controversy section. Net of evidence is that acute co-administration is fine and likely additive (caffeine + creatine in single workout sessions has been studied repeatedly with no blunting); chronic concurrent loading showed equivocal blunting in Vandenberghe 1996 but later studies didn't replicate. Practically: Dylan's V4 caffeine ramp doesn't conflict with creatine baseline.
• alcar / ALCAR: Mitochondrial bioenergetics + brain-tier carnitine. Both support brain ATP supply via different mechanisms (ALCAR: mitochondrial fatty acid oxidation; creatine: ATP buffering). Plausible synergy for brain energy under cognitive load. No clinical RCT directly testing the combination but mechanism is clean.
• carbohydrate (50-100 g) post-training: Modest insulin-driven uptake bump. Marginal; not worth restructuring eating around.
• HMB (β-hydroxy-β-methylbutyrate): Some additive effect on lean mass per Jowko 2001. Niche.
• L-glutamine: No documented synergy or antagonism. Both amino-acid-class metabolic support. Stack-safe.
• Modafinil + caffeine + L-theanine (Dylan's V5 cognitive stack): Creatine slots in as additive insurance for the energy substrate side; modafinil works on histamine/orexin/dopamine wakefulness, creatine works on ATP availability. No documented interaction, fully stack-safe.

Avoid stacking with

• Agmatine immediate co-administration: Per encyclopedia (line 640) — creatine may hinder agmatine absorption. Take separately by 2-3 hours. Both can be daily, just not in the same dose. Simple solution: creatine AM, agmatine PM (or vice versa).
• Nephrotoxic drugs (NSAIDs at high dose, aminoglycosides, etc.): Not an absolute contraindication but caution worth noting in the rare event of renal stress. Not relevant for Dylan.

Neutral / safe co-administration

• All V4 stack: NAC, citicoline, magnesium glycinate + threonate, DHA, PS, curcumin, rhodiola, theanine, glycine, D3+K2, beta-alanine, vitamin C — all stack-safe.
• All V5 planned: modafinil, bromantane, Adamax/Semax, ALCAR, apigenin, taurine, astaxanthin, l-tryptophan — all stack-safe.
• All electrolytes (sodium, potassium, magnesium): no interaction.
• Whey/casein/EAA protein supplements: no interaction.

• CYP enzymes: Creatine is not metabolized via CYP and does not induce or inhibit CYP enzymes. No clinically relevant CYP-mediated interactions with modafinil, bupropion, or other CYP-metabolized stack drugs.
• Caffeine (acute): No meaningful interaction. Both can be taken pre-workout or pre-cognitive-stress.
• Caffeine (chronic concurrent loading): Vandenberghe 1996 suggested chronic high-dose caffeine (5 mg/kg) might blunt creatine's performance effect during loading. Subsequent studies did not consistently replicate; the modern interpretation is that acute caffeine pre-workout doesn't blunt creatine, and chronic high caffeine probably doesn't matter much either at typical doses. For Dylan: V4 caffeine ramp + creatine baseline is fine.
• Diuretics: Theoretical interaction via cellular hydration changes. No documented clinical issue.
• NSAIDs: No interaction at typical doses. Stack-safe.
• Metformin / SGLT2 / antidiabetics: No interaction.
• Contraceptives: No interaction.
• Lithium: No documented interaction with creatine (unlike taurine). Stack-safe.
• Modafinil + creatine: No interaction documented; mechanistically independent (modafinil = histamine/orexin/dopamine wakefulness; creatine = ATP buffering). Likely complementary for sustained cognitive load.

The most relevant gene for creatine response is SLC6A8 (also called CT1 / CRT / creatine transporter), which moves creatine across the blood-brain barrier and into peripheral tissues.

• SLC6A8 deficiency syndrome: X-linked, mostly affects boys. Causes intellectual disability, autism, seizures, language impairment due to severely impaired brain creatine uptake. Oral creatine doesn't bypass the transporter; affected patients need creatine precursors (guanidinoacetate, arginine, glycine) instead. Rare (~1% of X-linked intellectual disability cases). Not a common variant in healthy populations.
• SLC6A8 polymorphisms in healthy adults: Limited direct PGx data on dose-response in healthy variants. Theoretical: lower-activity variants might show smaller cognitive response to standard 5 g/day chronic but still respond to high-dose acute (Forsberg-style 20 g pushes creatine across by mass action).
• GAMT and AGAT polymorphisms: Affect endogenous synthesis. Severe deficiencies are rare and clinically obvious (developmental delay). Subclinical variation is theoretical.
• MTHFR variants (C677T, A1298C): MTHFR polymorphisms affect methylation capacity; since endogenous creatine synthesis is methyl-intensive, MTHFR-variant carriers theoretically benefit more from supplementation (less SAM consumed for creatine synthesis = more SAM available for other methylation). Plausible mechanism, limited direct creatine-PGx RCT data.
• Vegetarian status (non-genetic but pharmacogenomically-similar): Vegetarians have lower baseline brain creatine and respond more strongly. Carnivores at full sleep have minimal cognitive response at 5 g/day. Dylan = carnivore at imperfect sleep — falls between these archetypes.
• 23andMe relevance for Dylan (results June 5-15, 2026): Check SLC6A8, GAMT, AGAT variants for completeness; check MTHFR variants for the methylation-pathway angle. Likely no actionable dosing change — the 5 g/day baseline is far above any plausible synthetic shortfall, and the Forsberg 20 g acute protocol pushes by mass action regardless of transporter variants.

Recommended for Dylan: BulkSupplements micronized creatine monohydrate via Amazon ($20-25 / 1.5 kg = ~$2/month at 5 g/day, or ~$3/month if going to 10 g/day). The marginal cost of running 10 g/day chronic instead of 5 g/day is trivially small — worth considering if he wants to push muscle pool fully saturated and start nudging brain pool toward saturation as well, without needing the Forsberg acute protocol.

For Forsberg high-dose acute protocol: same supplier, just measure out 20 g (~4 teaspoons of micronized powder) on use days, dissolve in hot water with food. No special form needed.

• Baseline (before starting): N/A for Dylan (already on creatine for years). For new users: weight, body composition (DXA or bioimpedance if available), serum creatinine, eGFR, cystatin C if available. CK if athletic context.
• During use:
  • Body weight — expect 1-2 kg gain in first 2-4 weeks (intracellular water).
  • Serum creatinine — will rise 5-15% as measurement artifact. Tell the lab you're on creatine. Use cystatin C as the cleaner kidney function marker if eGFR concerns arise.
  • Performance metrics — 1RM, repeated-sprint output, fatigue resistance. Effect detectable at 4-8 weeks.
  • For Forsberg acute protocol: subjective cognitive performance during the sleep-deprived window; if Dylan tracks reaction time / working memory via apps, baseline a non-creatine sleep-deprived day vs creatine-loaded sleep-deprived day for personal calibration.
• Post-cycle: Not applicable (not cycled).
• Dylan's June bloodwork window: flag to lab he's on creatine. Cystatin C ideal. Don't over-interpret elevated creatinine.