L-Threonine for Health & Longevity - Quick Reference Sheet
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L-Threonine for Health & Longevity

Created on 07/19/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 4.8 – Audit

An essential amino acid that most people already get in adequate amounts from protein-rich food. Extra intake is well tolerated with a wide safety margin, but added benefit is modest and largely unproven: small studies show a minor easing of muscle stiffness, while its promise for gut health and healthy aging rests mainly on animal research. (Full Review)

Protocol

Dose
1–4 g/day
Free-form L-Threonine for gut or general use; sits below the 12 g/day tested ceiling
Timing
With meals
Flexible; an evening dose is a reasonable option for any glycine-related calming effect
Frequency
Split 2–3×/day
For doses above ~3 g/day; single dosing is acceptable at lower intakes
Time to effect
Muscle stiffness
~2 weeks
Trials assessed anti-stiffness effects over roughly two-week periods
Gut & general
No set timeline
No established human timeline; effects should not be expected to be rapid or dramatic

Benefits

Contraindications
  • Significant kidney or liver impairment
  • Active inflammatory bowel disease flares
  • Rare inborn errors of amino-acid metabolism
  • Pregnancy or lactation (no established safe dose)
    •
Key Interactions
  • Glycine and serine supplements
  • Central anti-spasticity and sedative drugs (baclofen, tizanidine, diazepam, benzodiazepines)
  • Large neutral amino acids and protein/BCAA supplements (leucine, isoleucine, valine)
  • Vitamin B6
    •

Risk & Side Effects

  • High:
  • Medium:
  • Low: Transient, non-specific blood-marker elevations
    •
  • Speculative: Worsening of active inflammatory bowel disease flares; gastrointestinal discomfort at high doses; nitrogen load in kidney or liver impairment
    •

Monitoring

Marker Target Why
AST / ALT ≤ 25 U/L Detect the minor, non-specific liver-enzyme rise reported at higher doses
Creatine kinase (CK) 40–200 U/L Screen for the transient muscle-marker elevation seen at 9 g/day
eGFR > 90 mL/min/1.73m² Confirm kidney capacity to clear the nitrogen load before higher-dose use
BUN 10–16 mg/dL Gauge nitrogen load from amino-acid intake
Plasma amino-acid panel (threonine) Within lab reference interval Confirm adequacy or repletion, especially on low-protein diets

Cadence: Not required for low-dose use; for higher-dose or higher-risk users, baseline then ~4–8 weeks after starting and every 6–12 months, or sooner if symptoms arise

Qualitative Assessment

  • Muscle tone or stiffness in a neurological context — any easing of stiffness
  • Digestive comfort and stool quality — a rough proxy for gut tolerance
  • General energy and well-being
  • Absence of new gastrointestinal upset at the chosen dose
Not medical advice. Educational distillation of a single evidence review. Confirm any decision with a qualified clinician, especially in the presence of prescription drugs or chronic conditions.