InfoSynergy
L-Theanine
Theanine may smooth caffeine-related jitteriness while preserving attention benefits.
Recommendation: Common pairing at moderate doses, such as 100 mg caffeine with 200 mg theanine.
Caffeine
Other ·Strong evidence ·Reviewed May 2026
Caffeine is a well-studied stimulant and ergogenic aid that improves alertness, vigilance, endurance, power, and perceived exertion in many settings. Benefits are dose-dependent but so are anxiety, insomnia, palpitations, and blood pressure effects. Adults generally should keep total caffeine near or below 400 mg/day, and pregnancy guidance is typically lower.
What it's good for
What to watch for
- Insomnia
- Anxiety or jitteriness
- Palpitations
- Uncontrolled arrhythmia or significant palpitations without clinician guidance
- Severe anxiety or panic disorder exacerbated by stimulants
The bottom line
Evidence rating strong. Most-documented uses: improves alertness and vigilance, improves endurance performance, can improve power and repeated effort. 3 sources indexed (2001–2021), with 5 interaction records on file.
The science
How it works, mechanistically.
Core mechanism
Caffeine antagonizes adenosine A1 and A2A receptors, reducing perceived fatigue and increasing arousal. It also increases catecholamine signaling, calcium handling in muscle, and central drive, which can improve endurance and power output. Genetic variation, habitual intake, sleep debt, anxiety sensitivity, and dosing time strongly influence response and adverse effects.1,2
Class
Adenosine receptor antagonist stimulant
Found in food
Coffee, Tea, Yerba mate
Low-status signs
No essential nutrient deficiency; withdrawal can cause headache, fatigue, irritability, low mood, and sleepiness
Dosing
Dosing & protocol.
Common range
1-3 mg/kg for focus or lower-side-effect use; 3-6 mg/kg 30-60 minutes pre-exercise for performance; keep total daily adult intake near or below 400 mg unless clinician-directed
Recommended form
Measured caffeine capsule, coffee, or low-sugar beverage with known caffeine content
Absorbs rapidly with peak effects often 30-60 minutes after ingestion. Food may slow onset but can improve tolerability.
Forms
Forms & what to buy.
Ranked by evidence and value.
Anhydrous Caffeine Capsule Recommended
Precise dosing and rapid absorption. Take 30-60 minutes before need; avoid late day.
Coffee
Food beverage with variable caffeine and polyphenols. Use known serving sizes when tracking intake.
Caffeine Gum
Buccal absorption can create faster onset. Use carefully to avoid redosing too soon.
Cost
What it actually costs.
Real-world pricing across three quality tiers. Assumes Anhydrous caffeine capsule.
BudgetBest value
$1 /mo
$0.03 per dose
Mid
$5 /mo
$0.15 per dose
Premium
$18 /mo
$0.60 per dose
Plain caffeine is inexpensive; beverages and gum cost more per effective dose. Updated 2026-06-04.
Goals
Goal-based dosing.
Endurance Performance
Timing: 30-60 minutes pre-exercise
Start at the low end to assess anxiety, GI, and sleep effects.
Focus and Vigilance
Dose: 50-200 mg3
Timing: Morning or early afternoon
Avoid using caffeine to compensate for chronic sleep deprivation.
Low-Side-Effect Training Boost
Dose: 1-3 mg/kg
Timing: 30-60 minutes pre-workout
Often enough for benefit with less jitteriness than higher doses.
Why people use it
Symptoms it's matched to.
Where this appears in the symptom-to-supplement map, ranked by relevance.
Sleepiness
82% relevance
Adenosine receptor antagonism increases alertness.
EnergyStrong evidenceCoffee or measured capsule
Avoid late-day use.
Poor workout intensity
75% relevance
Increases central drive and reduces perceived exertion.2
AthleticStrong evidenceAnhydrous caffeine
Trial dosing before events.
Protocols
Featured in protocols.
Evidence-based stacks that include it, with the exact dose and timing each one uses.
Athletic Performance Protocol
RecoveryOptionalStrong evidenceIntermediate$30-50/mo
Dose here
200 mg
Timing
30-60 min pre-workout
Blocks adenosine receptors reducing perceived exertion; enhances power, endurance, and reaction time
Endurance Performance Protocol
Athletic PerformanceCoreStrong evidenceIntermediate$45-75/mo
Dose here
3-6 mg/kg body weight
Timing
45-60 minutes before training or competition
Caffeine reduces perceived exertion and central fatigue while enhancing fat oxidation and endurance capacity across a wide range of aerobic events.3,1
Focus and Attention Protocol
CognitionCoreStrong evidenceBeginner$35-65/mo
Dose here
50-100 mg
Timing
Morning, with L-Theanine; avoid late-day dosing
A well-characterized adenosine antagonist that improves alertness, reaction time, and vigilance; combined with L-Theanine it delivers focus with fewer of the anxiety and crash effects seen with caffeine alone.
Strength and Hypertrophy Protocol
Athletic PerformanceOptionalStrong evidenceBeginner$45-80/mo
Dose here
3-6 mg/kg bodyweight
Timing
30-60 minutes before training
Caffeine acutely improves muscular strength, power, and reduces perceived exertion, helping sustain training intensity that drives strength and hypertrophy adaptations.1,2
Safety
Full safety detail.
Side effects
- Insomnia
- Anxiety or jitteriness
- Palpitations
- Increased blood pressure
- Reflux or stomach upset
- Headache or withdrawal symptoms
Contraindications
- Uncontrolled arrhythmia or significant palpitations without clinician guidance
- Severe anxiety or panic disorder exacerbated by stimulants
- Uncontrolled hypertension
- Pregnancy should follow obstetric caffeine limits
- Avoid late-day use in insomnia
Interactions
Interaction records.
ModerateConflict
Melatonin
Caffeine can delay sleep onset and counteract melatonin timing goals.
Recommendation: Avoid caffeine within 8-10 hours of planned sleep if insomnia-prone.
ModerateCaution
Rhodiola Rosea
Both can feel stimulating in some users and may increase anxiety or insomnia.
Recommendation: Start low and avoid late-day stacking.
ModerateCaution
Green Tea Extract
Many green tea extracts contain caffeine and concentrated EGCG, increasing stimulant and liver-safety concerns.
Recommendation: Check labels for caffeine and EGCG content and avoid duplicate high doses.
ModerateCaution
Panax Ginseng
Both Panax ginseng and caffeine can be mildly stimulating, and combining them may amplify CNS and cardiovascular stimulation in sensitive individuals.
Recommendation: Use caution when combining ginseng with high caffeine intake. Limit total stimulant load and avoid late-day dosing to protect sleep. Monitor for jitteriness, palpitations, or elevated blood pressure.
Sources
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Reviews & position papers
3- 1International society of sports nutrition position stand: caffeine and exercise performanceNeeds reviewNo linkGuest NS et al. · Journal of the International Society of Sports Nutrition · 2021
Caffeine improves endurance, muscular endurance, movement velocity, strength, sprinting, jumping, and sport-specific actions in many settings.
- 2International society of sports nutrition position stand: caffeine and performanceNeeds reviewNo linkGoldstein ER et al. · Journal of the International Society of Sports Nutrition · 2010
Evidence supports caffeine for endurance and high-intensity exercise with individualized dosing.
- 3Caffeine for the sustainment of mental task performance: formulations for military operationsNeeds reviewNo linkInstitute of Medicine Committee on Military Nutrition Research · National Academies Press · 2001
Caffeine can maintain vigilance and attention during sleep loss or sustained operations.
Keep exploring
Deep dives & adjacent profiles.
This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.
Use this with your stack
Caffeine in NutriStack.
Add it to your stack, see how it interacts with everything else you take, and get a Stack Score that updates the moment it does.