Three people's rhythm trouble on melatonin eased once they stopped
A 63-year-old on 10 mg a day developed a partial heart block that cleared after stopping. Two earlier cases, at 1 to 10 mg a day, are the only others found.
What the study found
In three reported cases, melatonin rhythm trouble eased on stopping
A 63-year-old man with a normal heart structure, on 10 mg of melatonin a day, developed a partial heart block and extra beats that cleared once he stopped. A search found two earlier cases of irregular beats, at 1 to 10 mg a day. Three cases mark a possible rare reaction, not a known risk.
The caveat · Three cases, no comparison group
With no comparison group and no count of people who took melatonin without trouble, the cases cannot give a rate. The link rests on timing and on recovery after stopping, with no formal causality score applied. Heart block is a rhythm problem, not heart failure.