Nicotinamide vs Nicotinic acid: what is the difference?

How they differ

Both are vitamin B3 and both end up as the same coenzyme, NAD, but they behave very differently on the way there. Niacin is nicotinic acid, carrying a carboxylic acid group, and at high intakes it causes the flush, a temporary reddening and prickling of the skin driven by prostaglandin release. Nicotinamide carries an amide instead and does not cause the flush at all, which is why supplements sold as flush-free use it. That same carboxylic acid is why niacin, and not nicotinamide, has effects on blood lipids. In skincare the amide form is the one used, listed as niacinamide, where it is studied for barrier function and pigmentation.

Side by side

Structural similarity 0.65 of 1, computed as a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.

Common questions

What is the difference between Nicotinamide and Nicotinic acid?

Both are vitamin B3 and both end up as the same coenzyme, NAD, but they behave very differently on the way there. Niacin is nicotinic acid, carrying a carboxylic acid group, and at high intakes it causes the flush, a temporary reddening and prickling of the skin driven by prostaglandin release. Nicotinamide carries an amide instead and does not cause the flush at all, which is why supplements sold as flush-free use it.

Is Nicotinamide bigger than Nicotinic acid?

Nicotinic acid is the heavier molecule, 123.11 g/mol against 122.12 g/mol for Nicotinamide. Nicotinamide is C6H6N2O and Nicotinic acid is C6H5NO2.

Which has the lower reported LD50, Nicotinamide or Nicotinic acid?

Nicotinamide, at 3,500 mg/kg (oral, rat), against 7,000 mg/kg (oral, rat) for Nicotinic acid. An LD50 is one acute animal measurement, and the two here were not necessarily measured in the same species, so it is a data point rather than a ranking of how dangerous either is to a person.