Enhanced mental focus and alertness
Significantly improves concentration, attention, and cognitive performance
Caffeine
Natural stimulant that enhances mental focus, alertness, and athletic performance through adenosine receptor antagonism
Scientific name1,3,7-trimethylxanthine
FormulaC8H10N4O2
Molecular weight194.19 g/mol
CAS58-08-2
99
absorption score
7
safety / 10
10
USD per month
5
documented interactions
Check it against something
Caffeine with:
- Amylase
- Ashwagandha
- Avocado Oil
- BCAA (Branched-Chain Amino Acids)
- Beetroot Powder
- Beta-Alanine
- Bifidobacterium lactis
- Bifidobacterium longum
- Bovine Collagen
- Calcium
- Calcium Bone Formula
- Calcium Carbonate
- Casein Protein
- Chicken Collagen
- Choline (Bitartrate)
- Chondroitin Sulfate
- Coconut Oil
- Collagen Peptides
- Comprehensive Immune Support Complex
- Comprehensive Multivitamin-Mineral Complex
- Creatine HCL
- Creatine Monohydrate
- D-Mannose
- DHA
- Electrolyte Blend
- EPA
- Fish Oil (EPA/DHA)
- Folate (5-MTHF)
- Ginger
- Iron Fumarate
- Iron Sulfate
- Joint Mobility Formula
- Keratin
- Krill Oil
- L-Carnitine
- L-Citrulline
- L-Theanine
- Lactase
- Lactobacillus acidophilus
- Lactobacillus rhamnosus
- Lipase
- Magnesium Citrate
- Magnesium Glycinate
- Magnesium Oxide
- Marine Collagen
- Melatonin
- Modafinil
- Olive Oil Extract
- Omega-3 + Curcumin + Vitamin D Triple Anti-Inflammatory Formula
- Papain
- Protease
- Saccharomyces boulardii
- Turmeric
- Vitamin B12 (Cyanocobalamin)
- Vitamin B12 (Methylcobalamin)
- Vitamin C (Ascorbic Acid)
- Vitamin C (Sodium Ascorbate)
- Vitamin D3
- Whey Protein
- Zinc Gluconate
Nothing found
94
out of 100
Works better together
Compatible. Timing differs, so follow each supplement's own window.
What it does
mechanism and evidence for each claimIncreased athletic performance and endurance
Improves exercise capacity, power output, and endurance performance
Enhanced fat burning and metabolism
Increases metabolic rate and promotes fat oxidation during exercise
Improved reaction time and motor control
Enhances reaction speed, coordination, and fine motor skills
Reduced fatigue and improved mood
Decreases subjective fatigue and enhances mood and motivation
Others take these for the same thing
Same goal, different mechanism — check any of them against this one
Creatine Monohydrate
Strength & power enhancement
3-5g
A
95%
Calcium
Bone health & muscle function
1,000-1,200 mg
A
30%
Magnesium Glycinate
Superior absorption sleep & muscle support
200-600 mg
A
90%
Vitamin B12 (Cyanocobalamin)
Energy & nerve support
250-1000 mcg
A
70%
Fish Oil (EPA/DHA)
Heart & brain health
1-2g EPA/DHA
A
85%
L-Theanine
Calm focus & stress relief
100-400mg
B
90%
Every pair we checked
12 combinations scored by the engine
Caffeine + Calcium Carbonate
High intake increases calcium excretion
Needs attention
58
Caffeine + Creatine Monohydrate
May blunt creatine's ergogenic effects when taken together acutely
Needs attention
61
Caffeine + Vitamin D3
No documented interaction either way
No known interaction
70
Caffeine + Whey Protein
No documented interaction either way
No known interaction
70
Caffeine + Lactase
No documented interaction either way
No known interaction
70
Caffeine + Bovine Collagen
No documented interaction either way
No known interaction
70
Caffeine + DHA
No documented interaction either way
No known interaction
70
Caffeine + Turmeric
No documented interaction either way
No known interaction
70
Caffeine + Fish Oil (EPA/DHA)
No documented interaction either way
No known interaction
70
Caffeine + Taurine
Enhanced endurance performance and reduced crash
Works better together
78
Caffeine + L-Tyrosine
Enhanced cognitive performance under stress
Works better together
78
Caffeine + L-Theanine
Reduces jitters while maintaining focus and alertness benefits
Works better together
94
Dosage
Daily100-400mg
Cognitive enhancement100-200mg as needed
Pre workout200-400mg 30-60 minutes before exercise
Fat burning100-400mg daily in divided doses
Alertness maintenance50-200mg every 4-6 hours as needed
When to expect it
First Effects15-30 minutes for alertness and focus enhancement
Peak Benefits30-60 minutes for maximum cognitive and performance benefits
Deficiency DevelopmentWithdrawal symptoms begin 12-24 hours after last dose
Toxicity OnsetOverdose symptoms possible with >500mg single dose
How to measure it
MarkerSerum caffeine levels (rarely measured clinically)
Optimal5-20 mg/L for performance benefits
Deficient belowNot applicable for stimulant
FrequencyOnly if toxicity suspected - monitor symptoms and tolerance instead
What people actually reported to the FDA
CAERS, 219 reports naming it as the suspectMost reported effects
Named as the suspect
219 reports
of 304 that mention it at all
Serious outcome
89%
hospitalisation, emergency room or worse
Other Serious or Important Medical Event175
Hospitalization45
Visited a Health Care Provider26
Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →
What actually reaches you
The label counts the carrier, your body does not
Absorption
Very high 99 of 100 · best absorbed form of this compound
Delivered daily
247.5 mg
Cost per 100 mg delivered
$0.13 comparative — uses the absorption score, not a measured percentage
Works better with
+
L Theanine
Reduces jitters while maintaining focus and alertness benefits
Theanine modulates caffeine's stimulating effects through GABA enhancement · level A
+
Taurine
Enhanced endurance performance and reduced crash
Taurine supports cellular hydration and energy metabolism · level B
+
Tyrosine
Enhanced cognitive performance under stress
Provides precursor for dopamine and norepinephrine synthesis · level BWhat not to take with Caffeine
!
Adenosine Supplements
Adenosine directly opposes caffeine's alertness effects
Competes for same adenosine receptors · major significance
!
Alcohol
Alcohol can mask caffeine effects and increase dehydration risk
Opposing CNS effects and diuretic interactions · moderate significanceMedication interactions
Discuss these with a pharmacist before combiningAdditive stimulant effects increasing side effect risk
What to do: Reduce caffeine intake when using stimulant medications
May enhance anticoagulant effects
What to do: Monitor for increased bleeding with high caffeine intake
May enhance effects and increase side effects
What to do: Monitor heart rate and adjust doses accordingly
Available forms
Caffeine Anhydrous (Pure Powder/Capsules): Precise dosing, Fast absorption, Cost-effective, Well-researched
Food sources
Coffee (8 oz)
80-120mg caffeine · 99
Black tea (8 oz)
40-70mg caffeine · 99
Green tea (8 oz)
25-50mg caffeine · 99
Caffeine supplements
100-200mg per capsule · 99
Too little
- Not applicable (stimulant, not essential nutrient):
- Withdrawal symptoms in regular users:
- Headache and fatigue
- Decreased alertness and focus
- Irritability and mood changes
- Reduced motivation and energy
- Difficulty concentrating
Too much
- Acute caffeine overdose symptoms:
- Severe anxiety and panic attacks
- Rapid heart rate and palpitations
- Nausea, vomiting, and diarrhea
- Tremors and muscle twitching
- Insomnia and agitation
- In extreme cases: seizures and cardiac arrhythmias
Who benefits most
athletes-endurance-sports
Proven ergogenic aid for endurance and power sports performance
3-6mg/kg body weight 30-60 minutes pre-exercise
students-professionals
Enhanced cognitive performance, focus, and alertness for mental tasks
100-200mg as needed for cognitive enhancement
weight-loss-goals
Increased metabolic rate and fat oxidation support weight management
100-400mg daily divided doses
shift-workers
Alertness and performance maintenance during irregular schedules
100-200mg as needed for alertness
pre-workout-enhancement
Comprehensive pre-workout benefits for training intensity and focus
200-400mg 30-45 minutes pre-workoutWhere to buy it
Look for Caffeine at 100-400mg per serving. The form that matters here is Caffeine Anhydrous (Pure Powder/Capsules).
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What else affects it
Beyond other supplements
!
Alcohol
Alcohol can mask caffeine effects and increase dehydration risk
Opposing CNS effects and diuretic interactionsHow it works
- Blocks adenosine A1 and A2A receptors preventing drowsiness and fatigue
- Increases cAMP levels leading to enhanced lipolysis and thermogenesis
- Enhances dopamine and norepinephrine neurotransmission in brain
- Improves calcium release from sarcoplasmic reticulum in muscle
- Inhibits phosphodiesterase enzymes maintaining elevated cAMP
- Modulates GABA neurotransmission affecting arousal and alertness
Key findings
what the evidence supports- Consistently effective ergogenic aid for endurance and power sports
- Significant cognitive enhancement with optimal dose 100-400mg
- Strong evidence for fat oxidation and metabolic enhancement
- Tolerance develops quickly but performance benefits remain
Sources: NIH Examine.com · data reviewed 2026-08-02
Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →
Common questions
What are the benefits of Caffeine?
Documented effects: Enhanced mental focus and alertness; Increased athletic performance and endurance; Enhanced fat burning and metabolism; Improved reaction time and motor control. Significantly improves concentration, attention, and cognitive performance
How much Caffeine should you take per day?
The common daily range is 100-400mg. By goal — cognitive enhancement: 100-200mg as needed; pre workout: 200-400mg 30-60 minutes before exercise; fat burning: 100-400mg daily in divided doses; alertness maintenance: 50-200mg every 4-6 hours as needed.
When is the best time to take Caffeine?
Morning or pre workout. First effects are typically reported within 15-30 minutes for alertness and focus enhancement.
What are the side effects of Caffeine?
At excessive doses: Acute caffeine overdose symptoms:, Severe anxiety and panic attacks, Rapid heart rate and palpitations, Nausea, vomiting, and diarrhea, Tremors and muscle twitching. Safety rating at normal doses is 7 out of 10.
What should you not take with Caffeine?
Separate it from Adenosine Supplements, Alcohol by two to four hours. Adenosine directly opposes caffeine's alertness effects
Does Caffeine interact with medications?
Documented interactions with stimulant-medications, blood-thinners, bronchodilators. Discuss these with a pharmacist before combining.
How do you know if you need Caffeine?
The marker is Serum caffeine levels (rarely measured clinically), optimal range 5-20 mg/L for performance benefits. Common deficiency signs: Not applicable (stimulant, not essential nutrient):, Withdrawal symptoms in regular users:, Headache and fatigue, Decreased alertness and focus.