How Long Does Circadin (Melatonin) Take to Work?
Circadin is the only UK-licensed prescription melatonin for primary insomnia in adults over 55. This guide explains its 2mg prolonged-release formulation's efficacy timeline.
Key Takeaways
- Onset: 1-2 hours (take 30-60 mins before desired sleep time)
- Peak effect: 3 hours post-dose
- Duration: 6-8 hours (mimics natural melatonin secretion)
- Optimal use: Combine with sleep hygiene for best results
- Safety: Contraindicated in autoimmune diseases and pregnancy
How Circadin Works
Circadin's prolonged-release formulation mimics the body's natural melatonin secretion:
Biological Action
- MT1 receptors: Promote sleep onset by lowering core body temperature
- MT2 receptors: Regulate circadian phase timing
Key difference: Unlike immediate-release melatonin, Circadin maintains therapeutic levels for 6-8 hours, making it ideal for sleep maintenance.
Circadin Efficacy Timeline
| Time After Dose | Pharmacological Stage | Patient Experience |
|---|---|---|
| 0-30 mins | Tablet dissolution begins | No noticeable effects |
| 1-2 hours | Threshold concentration (0.3-0.5 ng/mL) | Drowsiness begins |
| 3 hours | Peak concentration (1.6 ng/mL) | Deepest sleep phase |
| 6-8 hours | Gradual elimination (t½=3.5h) | Natural waking |
Dosage Guidelines
- Standard dose: 1 tablet (2mg) 1-2 hours before bedtime
- Administration: Swallow whole with water - do not crush/chew
- Duration: Maximum 13 weeks unless advised by GP
Optimizing Absorption
- Take after a light meal (high-fat foods delay absorption by 1.5h)
- Avoid caffeine after 3pm
- Maintain consistent bedtime routine
Potential Side Effects
Common (≥1/100)
- Headache
- Dizziness
- Nausea
Rare (<1/1000)
- Vivid dreams
- Mood changes
- Hypertension
Frequently Asked Questions
Can I take Circadin with sleeping pills?
No. Combining with other sedatives (e.g., zopiclone) increases drowsiness risks. Always consult your GP first.
Why isn't Circadin working for me?
It may be less effective for secondary insomnia (caused by pain/depression). Optimize sleep hygiene and consult your GP.
Can I cut Circadin tablets in half?
No. This damages the prolonged-release coating, causing rapid absorption and reduced efficacy.
Is Circadin addictive?
No evidence of dependence, but rebound insomnia may occur if stopped abruptly after long-term use.
Can I take it for jet lag?
Not recommended. Circadin is licensed only for primary insomnia in adults over 55.
Need Treatment for Jet Lag
If you're experiencing sleep difficulties, our UK-registered doctors can help determine if Circadin (Melatonin) Tablets is appropriate for your condition through a confidential online consultation.
Secure Prescription & Next-Day Delivery
MHRA-compliant | GPhC-registered pharmacy | Discreet packaging
Start UTI ConsultationRelated Guides
Medical Content Manager
Nabeel is a co-founder and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Feroz is a GMC-registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co-founder and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 29 October 2025
Next Review: 30 April 2026
Published on: 29 October 2025
Last Updated: 30 October 2025
