Getting the right dose of red light therapy is crucial for effectiveness. Here’s how to calculate your optimal dose.

The Biphasic Dose Response

The Arndt-Schulz Law applies to RLT:

  • Too little — No effect
  • Optimal — Maximum benefit
  • Too much — Reduced benefit or inhibition

More is NOT always better. There’s an optimal dose range.

Key Dosing Parameters

1. Irradiance (Power Density)

  • Measured in mW/cm²
  • How much light power reaches your skin
  • Higher irradiance = shorter treatment time

Optimal range: 30-100 mW/cm² at treatment distance

2. Energy Density (Dose)

  • Measured in J/cm²
  • Total energy delivered to tissue
  • Irradiance × Time = Energy Density

Optimal range: 1-60 J/cm² depending on condition

3. Distance

  • Light intensity decreases with distance (inverse square law)
  • Closer = more intense
  • 6 inches is standard for most devices

Dosing by Condition

Condition Irradiance Time Dose (J/cm²)
Skin health 30-50 mW/cm² 5-10 min 3-10
Pain relief 50-100 mW/cm² 10-15 min 10-60
Wound healing 30-50 mW/cm² 5-10 min 3-10
Deep tissue 100+ mW/cm² 10-20 min 20-60
Hair growth 30-50 mW/cm² 10-15 min 5-15

How to Calculate Your Dose

Formula: Dose (J/cm²) = Irradiance (mW/cm²) × Time (seconds) / 1000

Example:

  • Device irradiance: 50 mW/cm² at 6 inches
  • Treatment time: 10 minutes (600 seconds)
  • Dose: 50 × 600 / 1000 = 30 J/cm²

Common Dosing Mistakes

❌ Too close, too long

  • Causes excessive heat
  • Can inhibit cellular response
  • Follow manufacturer guidelines

❌ Too far away

  • Insufficient irradiance
  • No therapeutic effect
  • Maintain recommended distance

❌ Inconsistent dosing

  • Sporadic treatment gives poor results
  • Consistent daily use is key