Medical Disclaimer

1. Not medical advice

All content on Caffeine Math — including the calculators, the caffeine database, the guides, and the FAQ — is provided for general informational purposes only. It is not medical advice, diagnosis, or treatment, and it should not be relied upon as such.

Nothing on this Site replaces consultation with a qualified healthcare provider. Always seek the advice of your physician or another qualified health provider with any questions you may have about a medical condition, caffeine tolerance, or interactions between caffeine and any medications you take.

Never disregard professional medical advice or delay seeking it because of something you have read on this Site.

2. Caffeine data accuracy

The caffeine values displayed in our database and used by our calculators are typical averages drawn from public sources including the USDA FoodData Central database, FDA guidance, EFSA, manufacturer-published nutrition labels, and peer-reviewed research. Actual caffeine content can vary by 20% or more depending on:

• Brew method (espresso vs drip vs cold brew vs French press)
• Brew strength (coffee-to-water ratio)
• Bean variety (Arabica ~1.2% caffeine vs Robusta ~2.2%)
• Roast level (lighter roasts retain slightly more caffeine)
• Serving size (a "cup" can mean 6 oz or 20 oz)
• Brand formulation (energy drinks vary batch-to-batch)
• Steep time and water temperature (for tea)

Treat all displayed values as estimates. For precision, check the product label.

3. Safe-limit calculations are general guidance

The 400 mg/day limit for healthy adults comes from the FDA. The 200 mg/day limit for pregnant women comes from ACOG. The 100 mg/day limit for adolescents comes from the AAP. These are general population-level guidelines — they reflect what is safe for most people in that demographic.

Your personal tolerance may be meaningfully lower. Common reasons include:

• Genetics: Variations in the CYP1A2 gene split people into "fast" and "slow" metabolizers. Slow metabolizers may experience negative effects well below 400 mg.
• Body weight: Caffeine affects smaller people more per mg/kg. Our body-weight calculator provides a more individualized estimate.
• Medications: Certain antibiotics (ciprofloxacin), antidepressants (fluvoxamine), and thyroid medications slow caffeine metabolism.
• Pregnancy: Caffeine half-life stretches from 5 hours to 11 hours in the third trimester.
• Smoking: Smokers metabolize caffeine faster (half-life ~3 hours); quitting roughly doubles the half-life overnight.
• Age: Newborns metabolize caffeine very slowly (half-life up to 80 hours). Adults over 65 may also metabolize it more slowly.
• Liver disease: Severe cirrhosis can extend half-life to 50+ hours.
• Health conditions: Anxiety, hypertension, arrhythmia, GERD, and IBS can all be worsened by caffeine at doses well below the FDA limit.

4. Calculator limitations

Our calculators use simplified mathematical models:

• The half-life calculator uses a first-order decay model: C(t) = C₀ × 0.5^(t / h). This is the standard pharmacokinetic approximation but does not account for individual variation.
• The withdrawal timeline reflects DSM-5 typical symptom patterns. Individual symptoms may be milder or more severe, and may resolve faster or slower.
• The body-weight calculator uses 3–6 mg/kg from sports-nutrition research, capped at the FDA's 400 mg/day limit. This is not an FDA-validated formula.
• The brew-ratio calculator's caffeine estimate assumes ~90% extraction efficiency for drip brew and uses Arabica (12 mg/g) or Robusta (22 mg/g) reference values.

5. Emergency situations

If you suspect caffeine overdose, seek emergency medical attention immediately. Symptoms of caffeine overdose include:

• Rapid, irregular, or pounding heartbeat
• Chest pain or tightness
• Severe anxiety, panic attacks, or agitation
• Tremors or muscle twitching
• Nausea, vomiting, or diarrhea
• Confusion or hallucinations
• Seizures
• Difficulty breathing

In the United States, call 911 or Poison Control (1-800-222-1222). In the EU, call 112. In the UK, call 999.

6. Special populations

Pregnancy and breastfeeding

ACOG recommends limiting caffeine to ≤200 mg/day during pregnancy to reduce the risk of miscarriage and low birth weight. Caffeine passes into breast milk in small amounts; most lactation consultants consider ≤200 mg/day safe for nursing mothers, but monitor the baby for irritability or poor sleep. See our caffeine & pregnancy guide for details.

Children and adolescents

The AAP recommends children under 12 avoid caffeine entirely and adolescents 12–18 limit intake to ≤100 mg/day. Caffeine affects the developing nervous and cardiovascular systems more strongly, and is linked to sleep disruption, anxiety, and dependence in adolescents.

People with health conditions

If you have any of the following, talk to your doctor before consuming caffeine:

• Heart disease, high blood pressure, arrhythmias
• Anxiety, panic, or PTSD
• GERD, acid reflux, or peptic ulcers
• Irritable bowel syndrome (IBS)
• Seizure disorders
• Liver disease
• Osteoporosis (caffeine can reduce calcium absorption)
• Diabetes (caffeine can affect insulin sensitivity)

7. Liability

You use this Site and its tools at your own risk. We are not liable for any health consequences, decisions, or actions taken based on information from this Site. See Section 7 of our Terms of Service for the full limitation of liability.

8. Updates to this disclaimer

We may update this disclaimer when our content changes or when new research shifts the consensus on caffeine safety. The "Last updated" date at the top of this page reflects the most recent revision.