I Built a "Lethal Dose" Calculator for Herbs — Here's What LD50 Data Reveals About Safety

We've all heard "natural is safe." But is it? How much green tea extract would actually kill you? What about that St. John's wort supplement?

I built a free Lethal Dose Calculator at Botánica Andina to answer this question using LD50 data — the scientific measure of what kills 50% of a test population. The results are surprising.

What is LD50?

LD50 = "Lethal Dose, 50%" — the dose that would kill half the people who take it.

It's measured in mg/kg of body weight. Lower LD50 = more toxic.

Substance	LD50 (mg/kg)	What This Means
Caffeine	192	~15g for 150lb person = 100+ espressos
Nicotine	0.5	~75mg for 150lb person = 1-2 cigarettes (pure)
Water	6,000	~450g for 150lb person = ~18 liters

The Calculator

The tool takes:

1. Your body weight
2. A herb/supplement from the database (25+ substances)
3. The form (capsule, tea, extract)

And calculates:

• Lethal dose in your unit of choice
• Number of doses to reach it
• Safety margin (therapeutic dose / lethal dose)
• Color-coded warning level

What I Found Building This

1. Some "Natural" Things Are Scary Toxic

Comfrey root tea? LD50 = 1200 mg/kg. That's low.
Kava kava extract? Even lower.

The tool shows you exactly how many cups or capsules it would take. It puts numbers to "be careful."

2. Coffee Is Surprisingly Safe (In Lethal Terms)

LD50 of caffeine is 192 mg/kg. For a 150lb person:

• Lethal dose = ~13g
• One espresso has ~63mg
• You'd need ~200+ espressos

You'd vomit or have a heart attack long before reaching lethal levels.

3. Supplements Vary Wildly in Concentration

This is where it gets dangerous. The same herb in different forms:

Form	Potency
Dried herb tea	1x (baseline)
Tincture (1:5)	5x
4:1 extract	4x
10:1 extract	10x

One "natural" capsule could be 10x more potent than loose tea.

How the Calculator Works

The math uses FDA inter-species scaling:

human_LD50 = animal_LD50 × (human_weight / animal_weight)^0.67

Then it converts to your chosen unit:

• Capsule count (based on typical 500mg dose)
• Tea cups (2g dried herb per cup)
• Dropperfuls of tincture
• Milliliters of extract

The Data Sources

LD50 values came from:

• PubChem (NIH chemical database)
• TOXNET (toxicology data network)
• ECHA (European Chemicals Agency)
• Peer-reviewed toxicology papers

Only high-quality data included. No anecdotes.

Controversy: Is This Tool Safe to Publish?

Some feedback: "This could encourage dangerous behavior."

My take: No. People will Google "how much X is dangerous" regardless. Providing accurate, scientific data is better than them finding misinformation.

The tool includes prominent disclaimers:

• This is educational, not dosing advice
• LD50 is a population statistic, not a guarantee
• Real toxicity varies by age, health, interactions
• Always consult a professional

Technical Details

Frontend

• Vanilla JavaScript for calculations
• Real-time updates as user changes inputs
• Visual feedback (green → yellow → red)

Data Structure

const substances = {
  "caffeine": {
    name: "Caffeine",
    ld50_mg_per_kg: 192,
    source: "PubChem",
    notes: "Coffee, tea, energy drinks"
  },
  "st_johns_wort": {
    name: "St. John's Wort",
    ld50_mg_per_kg: 2000,
    source: "ECHA",
    notes: "Herbal extract"
  }
  // ... 23 more
}

Safety Calculations

The tool calculates three metrics:

1. Absolute lethality - how many units to kill
2. Safety margin - therapeutic / lethal ratio
3. Warning level - based on substance class

What Users Learn

The educational value isn't "how much can I take" — it's:

Perspective

• Seeing how many "safe" things are actually toxic in large doses
• Understanding why dosing matters
• Recognizing potency variations

Awareness

• Some supplements have narrow safety margins
• "Natural" ≠ automatically safe
• Concentrated extracts ≠ whole herbs

Responsibility

• This is why we talk to doctors
• This is why we follow dosing guidelines
• This is why we report supplements we take

Future Enhancements

• Add drug-herb interaction warnings alongside lethality
• Include chronic toxicity data (what happens with long-term use)
• Add more substances (currently 25+)
• Mobile app version

Try It

Visit botanicaandina.com for our full collection of free health tools based on scientific research.

Check the Lethal Dose Calculator at Botánica Andina — educational, eye-opening, and completely free.

Technical Note

The tool is open-source and data is transparent. If you spot errors or have additional LD50 data, the information is all in the GitHub repository.

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Built by Botánica Andina — visit botanicaandina.com for more free health tools — a free resource for evidence-based herbal information based on scientific research and Andean botanical knowledge.