The recommended daily dosage of niacin is 16mg (males) or 14mg (females), with a maximum dosage of 35mg, beyond which you end up with a niacin flush. Niacin flushes are not dangerous, but they can be uncomfortable.
Niacin is a precursor for (it turns into) nicotinamide mononucleotide (NMN), which in turn is a precursor for nicotinamide adenine dinucleotide (NAD), which helps your DNA repair itself.
The nutritional need for niacin was first noted in 1937, 100 years after its first discovery, after a long chase for the cause and cure of Pellegra in the US.
Studies found that high-dosage niacin can reduce high cholesterol levels (hypercholesterolemia). The niacin dosage for high cholesterol is 1-6 grams of niacin daily, starting from a lower 100mg per day and increasing steadily. This is best done using a slow-release supplement, which will reduce the “hit” that the body receives, thus lowering the effect of the niacin flush.
High dosages of niacin cause liver damage, with symptoms of jaundice, itching, nausea, vomiting and fatigue. However, the damage is usually mild, and will stop as soon as the niacin overdosage is stopped.