Report any unusual or persistent symptoms to your care team, and seek prompt medical attention for severe reactions such as difficulty breathing, chest pain, or signs of an allergic reaction
Uncommon side effects include constipation, diarrhea, irregular heartbeat, fatigue, and anxiety
Darker, pigmented patches or sunspots can temporarily darken, and then peel off over a week or so, leaving normal skin
Some users report flushing, similar to niacin, though this is less common with NR and NMN than with nicotinic acid
It always arrives promptly
Reported / Possible Side Effects Mild, anecdotal: Occasional reports of mild headache, transient jitteriness, or injection-site reactions