While most people do not experience any side effects from Circadan, there are some mild side effects. If they worsen or persist, talking to a pharmacist or healthcare provider is advisable.

• Sleepiness or feeling tired  during the daytime
• Headache
• Stomach ache
• Nausea
• Dizziness
• Feeling irritable or restless
• Dry mouth
• Dry or itchy skin
• Pains in the arms or legs
• Strange dreams
• Night sweats

Very rarely, more serious side effects have been reported. If any of these are experienced, it should be reported to a doctor immediately: 

• Feelings of depression
• Blurred vision
• Feeling faint or passing out
• Experiencing vertigo (when the room seems to be spinning around)
• Persistent bleeding, unexplained bruising or blood in the urine.

In very rare cases, melatonin can induce an anaphylactic allergic reaction. Go immediately to an emergency room or call for medical help if any of the following signs are observed:

• A skin rash that includes itchy, red, swollen, blistered or peeling skin
• Wheezing together with tightness in the chest or throat
• Having trouble breathing or talking
• Swelling of the mouth, face, lips, tongue or throat.

Please take time to read the manufacturer’s Product Insert that comes with the medication. Not all side effects are listed here. Consult a healthcare provider if you experience these or other unexpected effects.

Circadin can be used as a dietary supplement that acts to combat insomnia. It is not itself a sleeping medication, but works by regulating the timing of the overall sleep-wake cycle. It helps to set the 24-hour internal timekeeper (the circadian clock) that the body uses to judge roughly what the time of day is for synchronization with the outside world.

There are also potential areas where melatonin can provide extended benefits when biological rhythms are disturbed, such as jet lag, insomnia in blind or elderly people, delayed sleep phase syndrome or for shift workers. 

In addition to improving sleep, it is also reported that melatonin is involved in managing immune functions, blood pressure and cortisol levels. Studies have also shown that melatonin may slow down macular degeneration, reduce symptoms of seasonal affective disorder (SAD) and even provide relief for people suffering from Gastro-Esophageal Reflux Disease (GARD). Doctors can precribe Circadin off-label for patients with these or any other conditions that melatonin can address.

Read more about some of the main and off-label functions of melatonin use here and here.