L-Tyrosine is an amino acid the body turns into dopamine, noradrenaline, and thyroid hormones. Its clearest effect is narrow: a large single dose before a demanding event helps protect memory and thinking during acute strain from cold, noise, or lost sleep. At rest, for mood, or for endurance, benefits are weak or absent. (Full Review)

Protocol

Dose

500–2,000 mg

Study effects seen at ~100–150 mg/kg (7–12 g)

Timing

30–60 min before

Ahead of the stressor or cognitive demand

Pattern

Single pre-task dose

Situational, morning or pre-task; not daily maintenance

Time to effect

Cognitive effect

30–90 min

Acute, following a pre-task dose

Plasma rise

1–2 hours

Tyrosine levels peak after a dose

Duration

Several hours

Single window; no cumulative benefit

Benefits

Medium: Preserved cognitive performance under acute stress

Low: Cognitive flexibility and multitasking; acute stress and mood buffering; thyroid hormone substrate support

Speculative: Age-related cognitive support; catecholamine support in dopamine-related states

Contraindications

MAOIs (phenelzine, tranylcypromine, selegiline)

Overactive thyroid (hyperthyroidism, Graves' disease)

Active malignant melanoma

Poorly controlled hypertension

Pregnancy or breastfeeding

Key Interactions

Levodopa / carbidopa-levodopa

Thyroid hormone medication (levothyroxine)

Stimulants and catecholaminergic agents (pseudoephedrine, caffeine, ADHD medications)

Additive supplements (caffeine, green tea extract, Mucuna pruriens)

High-protein meals and large neutral amino acids (branched-chain amino acids, tryptophan, phenylalanine)

Risk & Side Effects

Medium: Overstimulation, anxiety, and sleep disruption

Low: Gastrointestinal upset; blood pressure elevation; headache

Speculative: Thyroid overstimulation; melanoma growth concern

Monitoring

Marker	Target	Why
TSH	1.0–2.0 mIU/L	Screens thyroid status
Free T4 & Free T3	Upper-mid reference range	Confirms thyroid output if TSH abnormal
Blood pressure	<120/80 mmHg	Detects catecholamine-driven pressure rises
Resting heart rate	50–70 bpm	Flags overstimulation from noradrenergic effect

Cadence: Baseline; reassess thyroid and blood pressure at ~3 months if frequent or high-dose, then every 6–12 months; sooner if symptoms (palpitations, anxiety, insomnia)

Qualitative Assessment

Focus and task performance during stress, cold, or sleep loss
Alertness and drive during the target window
Sleep quality, noting any delay or lighter sleep from late or excess dosing
Anxiety or jitteriness signalling overstimulation

L-Tyrosine for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment