Circadin Side Effects: Complete Safety Guide
When Do Side Effects Start? How Long Do They Last? Timeline, Contraindications & Food Interactions
Table of Contents
- Key Takeaways
- Common Circadin Side Effects
- When Do Circadin Side Effects Start?
- How Long Do Circadin Side Effects Last?
- Side Effects Timeline: Day by Day
- Contraindications: Who Should NOT Take Circadin?
- Food Interactions with Circadin
- Serious Side Effects (Rare) – When to Seek Help
- Circadin Side Effects FAQs
Key Takeaways: Circadin Side Effects
- Most common: Headache, drowsiness, nausea, dizziness – usually mild and temporary.
- Start: Side effects typically appear within the first few days of treatment.
- Duration: Most resolve within a few days as your body adjusts; if persistent, consult your doctor.
- Contraindications: Avoid if allergic, pregnant, breastfeeding, severe liver/kidney disease, or autoimmune conditions.
- Food: Take after food; avoid alcohol – it can worsen drowsiness and reduce effectiveness.
- Emergency: Chest pain, fainting, visual changes, or allergic reactions require immediate medical attention.
Circadin (melatonin) is generally well tolerated, but like all medicines, it can cause side effects. This complete safety guide explains what to expect, when, and what to do.
Important Medical Advice
If you experience chest pain, fainting, severe dizziness, swelling of the face or tongue, visual changes, or an erection lasting more than 4 hours (very rare), stop Circadin and seek immediate medical help. Do not drive if you feel drowsy. Always consult your doctor before starting melatonin, especially if you have liver/kidney problems, an autoimmune disease, or are taking other medications.
Common Circadin Side Effects
According to the patient information leaflet, the following side effects are uncommon (may affect up to 1 in 100 people) but have been reported:
- Irritability, nervousness, restlessness
- Abnormal dreams, nightmares, anxiety
- Migraine, headache
- Lethargy (tiredness, lack of energy)
- Dizziness
- High blood pressure
- Upper abdominal pain, indigestion, nausea
- Dry mouth
- Inflammation of the skin, night sweats, itching, rash
- Pain in extremities
- Menopausal symptoms
- Feeling of weakness
- Weight increase
Most of these are mild and often improve as your body gets used to the medicine.
When Do Circadin Side Effects Start?
Side effects from Circadin usually begin within the first few days of treatment. Because melatonin works on the body's natural sleep‑wake cycle, some people may notice drowsiness or headache after the very first dose. Others may take a few days to adapt.
If you experience side effects that start after several weeks, consider whether any other factor (new medication, illness) might be the cause, and consult your doctor.
How Long Do Circadin Side Effects Last?
Most common side effects are temporary and resolve within a few days to a week as your body adjusts to the medicine. For example:
- Headache or dizziness: Usually improves after 3‑5 days.
- Nausea: Often subsides within the first week.
- Morning drowsiness: May persist if you take Circadin too late; adjusting the timing can help.
If side effects last longer than two weeks or become bothersome, speak to your doctor – a different dose or alternative treatment may be needed.
Side Effects Timeline: Day by Day
| Timeframe | What to expect |
|---|---|
| Days 1‑3 | Possible mild headache, drowsiness, or nausea as your body adjusts. These are usually transient. |
| Days 4‑7 | Most people adapt; side effects often diminish or disappear. |
| Week 2‑4 | If side effects persist beyond two weeks, consult your doctor. It may not be the right medicine for you. |
| After stopping | No withdrawal effects are known, but sleep patterns may return to baseline. |
Contraindications: Who Should NOT Take Circadin?
Do NOT take Circadin if:
- You are allergic to melatonin or any of the tablet ingredients (see PIL).
- You have severe liver disease – no studies, use not recommended.
- You have an autoimmune disease (e.g., multiple sclerosis, lupus) – safety not established.
- You are pregnant, trying to become pregnant, or breastfeeding.
- You are under 55 years old – other melatonin products may be used under specialist advice.
Consult your doctor before use if: you have mild‑to‑moderate liver/kidney problems, take other medications (especially fluvoxamine, cimetidine, oestrogens, rifampicin), or smoke (smoking can reduce effectiveness).
Food Interactions with Circadin
Take Circadin after food. The PIL states: “Take Circadin after you have eaten.” Food slows absorption slightly, which helps maintain the prolonged‑release profile and may reduce the chance of nausea.
Alcohol: Do not drink alcohol before, during, or after taking Circadin. Alcohol reduces the effectiveness of melatonin and can increase drowsiness and dizziness.
Caffeine: Caffeine is a stimulant and may counteract melatonin's sleep effects. Avoid caffeine in the evening.
Serious Side Effects (Rare) – When to Seek Help
Although uncommon, the following side effects require immediate medical attention (stop Circadin and contact a doctor):
- Chest pain (uncommon)
- Loss of consciousness or fainting (rare)
- Severe chest pain due to angina (rare)
- Feeling your heartbeat (palpitations) (rare)
- Depression, visual impairment, blurred vision, disorientation (rare)
- Vertigo (severe dizziness) (rare)
- Presence of red blood cells in urine, reduced blood cells (rare)
- Psoriasis (rare)
- Signs of allergy: swelling of mouth/tongue, difficulty breathing (frequency not known)
🗒️ MHRA Yellow Card: If you experience any side effect, you can report it directly via the Yellow Card scheme – this helps improve safety for everyone.
Circadin Side Effects FAQs
Can Circadin cause weight gain?
Weight increase is listed as an uncommon side effect. If you notice unexplained weight gain, discuss it with your doctor – it may be due to other factors.
Does Circadin cause depression?
Depression is a rare side effect. If you experience low mood, stop Circadin and consult your doctor immediately.
Can I take Circadin with blood pressure medication?
Some blood pressure medicines (adrenergic agonists/antagonists) may interact with melatonin. Always inform your doctor about all medications you take.
Is it safe to take Circadin every night for months?
Circadin is approved for short‑term use up to 13 weeks. Long‑term use should be supervised by a doctor. Do not exceed the recommended duration without medical advice.
Can Circadin cause nightmares?
Abnormal dreams and nightmares are uncommon side effects. If they bother you, speak to your doctor – adjusting the dose or timing may help.
Need Help with Sleep? Circadin Could Be an Option
If you're 55 or over and have persistent insomnia, Circadin may help reset your sleep pattern. A UK‑registered doctor can assess your suitability through a quick online consultation.
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Clinical References & Sources
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: 16 February 2026
Next Review: 16 August 2026
Published on: 16 February 2026
Last Updated: 16 February 2026