Glossary

Sleep Onset Latency

Updated February 28, 2026

Sleep onset latency (SOL) is the objective measurement of the time it takes to transition from full wakefulness to the first stage of sleep. It is a key metric for evaluating sleep quality and the impact of late-day supplement usage.

Within Unfair, SOL is often utilized as a primary objective proxy for assessing whether evening stacks are effectively promoting relaxation, or conversely, if late-day stimulant use is causing disruption.

Tracking and impacts

A normal SOL for healthy adults typically ranges from 10 to 20 minutes.

• Prolonged SOL (>30 minutes): Frequently associated with insomnia, late caffeine intake, or excessive evening stimulation.
• Reduced SOL (<5 minutes): May indicate severe sleep debt or exhaustion.

When adjusting supplements like magnesium, late-day adaptogens, or sleep-specific compounds (e.g., melatonin), monitoring changes in SOL over a stack cycle provides clear, quantifiable feedback on the intervention's success.