• Onset: Subtle, building over 1-3 weeks of consistent dosing. Not an acute-feel compound.
• Day-to-day: Often imperceptible. The effect is tracked better by retrospective comparison (after a 2-week washout, when you reintroduce it, the contrast is clearer) than by acute "did I feel it today?" introspection. This is fundamentally different from caffeine, modafinil, or phenibut where the on/off contrast is instantaneous.
• Sleep markers: Many users (and the Hausenblas 2024 Oura data) report increased deep-sleep duration and more vivid dreams. The "Mg dreams" signal is consistent across all Mg forms when starting from a deficit; it tends to settle within 2-4 weeks.
• Cognitive markers: Sustained attention, slightly faster word-finding, reduced "tip-of-the-tongue" lag — but these are all noise-floor effects in healthy users without a structured test. Lopresti 2026's cognitive-age battery is the closest objectification of what users describe.
• Stress/anxiety: Subtle baseline-lowering, often described as "less jaggy after a hard day" rather than acute anxiolysis.
• No "lift" or stimulant feel. This is a structural / baseline-improvement tool, not a state-change tool. Users seeking acute cognitive boost will be disappointed; users running a multi-month protocol will more often notice the absence (if they stop) than the presence.
• GI tolerability: Excellent. Loose stool risk lower than Mg oxide or Mg citrate at equivalent elemental doses, comparable to Mg glycinate. The threonate counter-ion does not produce the osmotic-laxative effect that drives Mg-citrate's GI signal.

• Tolerance buildup: None documented. Long-term use (>6 months, 1-year extension data) shows no efficacy decay in animal models, and the cognitive RCT outcomes in older adults persisted through 12+ weeks of continuous dosing without dose escalation.
• Recommended cycle: None — Magtein is daily-safe, indefinite. The animal CSF-Mg washout data argues against intermittent dosing — if you stop, central Mg falls back to baseline within 1-2 weeks and the synaptic-density gains regress.
• Reset protocol: N/A. If you stop Magtein and lose the cognitive overlay, you simply restart and rebuild over 4-12 weeks.
• Sleep-only use cases: Some users take Magtein only as needed for stress-spike nights — physiologically suboptimal (you don't build the CSF-Mg steady state), and probably no better than a one-off Mg-glycinate dose for those nights. The structural benefits of Magtein require daily continuity.

Synergistic with

• magnesium-glycinate / magnesium-bisglycinate (Dylan's V4 pairing): This is the canonical pairing — Magtein for brain Mg, glycinate/bisglycinate for systemic Mg. Glycinate also brings glycine, a co-agonist at NMDARs and a mild sleep adjunct in its own right. No metabolic competition; both forms add to total elemental Mg.
• citicoline (Dylan's V4): Both are NMDAR-system modulators — Mg is the channel block, citicoline supports membrane phospholipid substrate (PC) for synaptic membrane integrity. Already paired in V4. Clean overlap.
• agmatine: Mg is voltage-dependent NMDA block; agmatine is a GluN2B-preferential channel modulator with anti-glutamate-excitotoxicity effects. Complementary not redundant.
• lithium-orotate (low-dose): Both are GSK-3β / brain-protection adjuncts at micro-mineral doses; complementary not redundant. Particularly relevant for Dylan's subconcussive-impact context (BJJ/MMA).
• n-acetyl-cysteine: Glutamate modulation upstream (via system Xc-); complementary to Mg's NMDAR-channel gating.
• L-tryptophan / glycine (sleep): Mg supports sleep architecture; tryptophan/glycine supply substrate for serotonin/melatonin and GABAergic tone.
• L-theanine (Dylan's V4 / community-data top pairing): Theanine modulates GABA and reduces stress-spike cortisol; Mg supports the substrate. Top community combo (253 reports).
• DHA / fish oil: Membrane fluidity + Mg-dependent enzymes both upstream of NMDAR plasticity.
• vitamin D3: Mg is required for the activation of vitamin D (Mg-dependent CYP-mediated 25-hydroxylation in liver). Mg deficiency can blunt the response to vitamin D supplementation. Pair both.
• vitamin B6 (P5P): Mg-B6 synergy is well-documented for sleep + mood — Zhang 2022 RCT formulation explicitly combined them.

Avoid stacking with

• High-dose calcium supplements (>1 g/day) at the same dose-time: Compete for absorption at TRPM6/7 transporters; separate by 2 h.
• Quinolone (ciprofloxacin, levofloxacin) or tetracycline (doxycycline) antibiotics: Mg chelates and reduces antibiotic absorption ~30-50%; separate by 2-4 h — dose Mg 2 h before or 4-6 h after the antibiotic.
• High-dose zinc (>30 mg) at same dose-time: Mild competitive absorption; separate by 2 h or take zinc with a different meal.

Neutral / safe co-administration

All other V4/V5 stack compounds. No known significant interactions with creatine, omega-3, vitamin D, NAC, citicoline, alpha-GPC, taurine, glycine, l-theanine, ashwagandha, or any of Dylan's standard daily supplements.

• Quinolone / tetracycline antibiotics: Reduced antibiotic absorption — separate by 2-4 h. Clinically significant.
• Bisphosphonates (alendronate, risedronate): Reduced bisphosphonate absorption — separate by 2 h.
• Levothyroxine / liothyronine: Reduced absorption — separate by 4 h. Rarely binding at Magtein doses but technically applies; relevant if Dylan ever ends up on thyroid hormone.
• Loop diuretics (furosemide) and thiazide diuretics: Increase urinary Mg loss — may need higher Mg dose to maintain repletion; check serum Mg if chronically dosed.
• Proton-pump inhibitors (omeprazole, esomeprazole, pantoprazole) — chronic use: Reduce intestinal Mg absorption (TRPM6/7 transporter interference); patients on chronic PPI therapy often Mg-deficient. Monitor Mg if PPIs are chronic.
• Gabapentin / pregabalin: Reduced gabapentinoid absorption (~20%) if co-administered; separate by 2 h. Additive CNS depression possible at high doses.
• Aminoglycoside antibiotics (gentamicin, tobramycin): Increased nephrotoxicity if Mg is depleted; supplementation actually helps here but check baseline serum Mg.
• Digoxin: Mg deficiency worsens digoxin toxicity; chronic Mg supplementation is generally protective. Maintain stable Mg dose if on digoxin.
• Renal-clearance drugs: No CYP interactions — Mg is not a CYP substrate, inducer, or inhibitor. Absorption interactions only.
• CNS depressants (benzodiazepines, Z-drugs, trazodone, mirtazapine, alcohol): Theoretical additive sedation at high evening doses. Practically irrelevant at standard 2 g Magtein/day for most users; relevant only if titrating multiple sleep aids together.

• TRPM6 / TRPM7 variants: TRPM6 (intestinal) and TRPM7 (renal + intestinal) are the rate-limiting Mg transporters. Loss-of-function rare-variant carriers (TRPM6 mutations cause hypomagnesemia with secondary hypocalcemia) need substantially higher Mg doses. Common SNPs (e.g., rs8042919, rs11144134) have modest effects on Mg homeostasis — not directly actionable without genotyping and a clinical Mg-deficit phenotype.
• CNNM2 variants: Affect renal Mg reabsorption. Loss-of-function = renal Mg wasting; gain-of-function rare. Relevant for diuretic-treated patients.
• SLC41A1: Cellular Mg efflux; common variants have small effects.
• COMT, BDNF, MTHFR: Indirect interactions — these don't change Mg pharmacokinetics but modulate the downstream cognitive-plasticity response. A Val158Val COMT user (slower dopamine clearance, more frontal noise) and a Met/Met BDNF user (lower activity-dependent BDNF) may experience smaller cognitive Magtein effects, though this is speculative.
• For Dylan (23andMe pending — results expected ~June 5-15 per memory): Once raw data lands, run TRPM6, CNNM2, BDNF, COMT through Promethease or a manual SNP lookup. If TRPM6 reduced-function variants surface, consider bumping total Mg dose (likely via glycinate rather than more Magtein, since the brain-targeting tool is unlikely to be the binding constraint on systemic repletion). If standard variants, V4 doses are appropriate.

For Dylan: Source Naturals Magtein in V4 is the optimal pick — licensed extract, mid-cost, reliable. No reason to change.

• Baseline (pre-supplementation or annually):
  • RBC magnesium — more accurate than serum Mg for body-Mg status (serum reflects acute regulation, not stores); target upper-half of reference range (~5.5-6.5 mg/dL in most US labs)
  • Serum Mg — quick check; insensitive but routine
  • Ionized Mg — most physiologically relevant if available (specialty labs); rarely ordered clinically
  • Subjective sleep quality (PSQI score) — establish baseline for tracking the sleep-arm effect
  • Cognitive baseline — Cambridge Brain Sciences online battery (used in Lopresti 2026), or any standardized digital cognitive battery, to enable retest comparison at 3 and 6 months
  • Anxiety baseline (DASS-21, GAD-7, or VAS) — particularly relevant for combined Mg-anxiolysis tracking
• During use:
  • RBC Mg at 3 and 6 months — should sit upper-half of reference range on combined Magtein + glycinate
  • Sleep quality reassessment at 4-6 weeks (subjective + Oura/ring data if available — Dylan has Colmi R06 rings via the ring-health platform)
  • Cognitive retest at 6 weeks (Lopresti dosing window) and 12 weeks (Liu dosing window)
• Post-cycle: N/A — daily-continuous protocol; no post-cycle markers.
• For Dylan specifically: The June 2026 bloodwork window is the natural inflection point. Order RBC Mg + ionized Mg if available alongside standard panel. Run a Cambridge Brain Sciences pretest now (baseline) and retest at 6 weeks to capture the cognitive-age delta the Lopresti RCT measured.