Vitamin B3 — also known as niacin, niacinamide, or nicotinic acid — is one of the eight essential B vitamins your body relies on for energy production, metabolic health, and cellular repair. But what does a B3 vitamin actually do in the body, and why does it matter for long-term health?
This guide breaks down the science of vitamin B3, how much you need, what happens when you don’t get enough, and how niacin supports everything from brain function to blood pressure and cholesterol metabolism.
What Is Vitamin B3?
Image from Tally Health
Vitamin B3 refers to either three related compounds: niacin (nicotinic acid) or, niacinamide (nicotinamide), and nicotinamide riboside. TheseAll three are converted into biologically active molecules called niacin equivalents, which your cells use to create:
NAD+ (nicotinamide adenine dinucleotide)
NADP (nicotinamide adenine dinucleotide phosphate)
These coenzymes power cellular metabolism, DNA repair, antioxidant defense, and hundreds of biochemical reactions.
Because vitamin B3 is a water-soluble vitamin, your body doesn’t store it — meaning you need regular dietary intake from foods or dietary supplements to maintain healthy levels.
What Does a B3 Vitamin Do in the Body?
Image from Tally Health
1. Supports Cellular Energy Production
Vitamin B3 is required to produce NAD+, a molecule that fuels mitochondrial energy production. Without enough niacin, cells can’t efficiently convert food into usable energy.
This is one reason why many people use NAD+ by Tally Health, which contains 1,000 mg of niacinamide (the flush-free form of vitamin B3) to support healthy NAD+ levels as they decline with age.
2. Helps Maintain Healthy Cholesterol & Blood Fat Levels
High-dose niacin therapy (typically prescription niacin or extended-release niacin tablets) has historically been used to:
Increase HDL cholesterol levels (“good” cholesterol)
Reduce LDL cholesterol
Lower triglyceride levels
While niacin can improve cholesterol levels, health professionals now use it more selectively because recent clinical trials found limited benefits for primary and secondary prevention of cardiovascular events when added to intensive statin therapy.
Still, niacin’s role in cholesterol metabolism remains scientifically established.
3. Supports Blood Vessel Function & Blood Pressure
Niacin helps blood vessels dilate, which may influence blood pressure and circulation. Some studies suggest adequate dietary niacin intake is associated with reduced high blood pressure risk, although results vary.
4. Boosts Brain Function & Healthy Aging
NAD+ derived from niacin plays a central role in:
Neuronal energy production
DNA repair
Cellular resilience
Cognitive performance
Low niacin intake has been linked to neurological issues in severe deficiency, and some research is exploring connections to Alzheimer’s disease and broader brain health.
What Happens When You Don’t Get Enough Niacin?
Image from Tally Health
Niacin deficiency is uncommon in developed countries but remains a concern in some developing countries. Severe niacin deficiency can lead to pellagra, a condition characterized by:
Digestive system issues
Skin rashes
Cognitive impairment
Low HDL levels, fatigue, and poor metabolic resilience can also occur with inadequate intake.
Foods rich in niacin — such as beef liver, poultry, tuna, mushrooms, peanuts, and fortified grains — are reliable sources. The Food and Nutrition Board and Dietary Reference Intakes (DRIs) provide recommended dietary allowance guidelines to help ensure adequate intake.
High Doses: Can You Take Too Much Niacin?
Image from Tally Health
While niacin has well-studied health benefits, high doses — especially from prescription niacin or extended-release tablets — may cause side effects such as:
Skin flushing
Low blood pressure
Glucose intolerance
Liver toxicity or liver damage
Increased uric acid levels
Because of these risks, therapeutic doses for cholesterol management should only be used under medical supervision.
Forms like niacinamide (found in many dietary supplements) do not typically cause flushing and are considered gentler on the digestive system.
Niacin in Pregnancy & Maternal Health
Image from Tally Health
Research suggests maternal dietary niacin intake may influence fetal development and DNA repair pathways. Getting enough niacin is essential during pregnancy, though large doses should be avoided unless recommended by a health professional.
Can Vitamin B3 Treat Acne or Skin Conditions?
Image from Tally Health
Topical and oral niacinamide are frequently studied for:
Supporting healthy skin barrier function
Reducing inflammation
Managing acne
Supporting recovery after UV exposure
It also may support lower non-melanoma skin cancer risk when combined with other treatment strategies.
Should You Take a Niacin Supplement?
For most people, a balanced diet provides enough niacin. But you may consider a supplement if you want to support:
Energy production
Healthy aging
Brain function
Skin health
Cholesterol levels (under medical guidance)
It’s important to distinguish between prescription niacin used to treat high cholesterol and standard over-the-counter niacin supplements that support cellular health.
The Bottom Line
Image from Tally Health
Vitamin B3 plays an essential role in your metabolism, blood vessels, cholesterol levels, and cellular energy — largely through its ability to support NAD+ production. Getting enough niacin is crucial, but more isn’t always better, especially when using high-dose therapeutic forms.
For everyday cellular health and healthy aging, options like NAD+ by Tally Health, which includes 1,000 mg of niacinamide, may help support optimal NAD+ levels without the drawbacks associated with large doses of nicotinic acid.
By understanding what a B3 vitamin does — and how it powers your body from the inside out — you can make better decisions for your health, longevity, and overall well-being.
References
Zhang et al. Emerging strategies, applications and challenges of targeting NAD+ in the clinic. Nat Aging 2025; https://doi.org/10.1038/s43587-025-00947-6
Zheng et al. NAD+ in COVID-19 and viral infections. Trends Immunol 2022; https://doi.org/10.1016/j.it.2022.02.001
Lautrup et al. NAD+ in Brain Aging and Neurodegenerative Disorders. Cell Metab 2019; https://doi.org/10.1016/j.cmet.2019.09.001
Kane and Sinclair. Sirtuins and NAD+ in the Development and Treatment of Metabolic and Cardiovascular Diseases. Circ Res 2018; https://doi.org/10.1161/circresaha.118.312498
Rajman et al. Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence. Cell Metab 2018; https://doi.org/10.1016/j.cmet.2018.02.011
What does vitamin B3 do in the body?
Vitamin B3 supports cellular energy production, metabolism, DNA repair, antioxidant defense, and overall cellular health by helping the body produce NAD+ and NADP, which power hundreds of biochemical reactions.
What happens if you don’t get enough niacin (vitamin B3)?
Severe niacin deficiency can lead to pellagra, which is characterized by digestive issues, skin rashes, and cognitive impairment. Inadequate intake may also contribute to fatigue, low HDL cholesterol, and poor metabolic resilience.
How much vitamin B3 do adults need per day?
Most adults need between 14–16 mg of vitamin B3 per day, according to recommended dietary allowance guidelines, though many people consume more through diet, fortified foods, and supplements.
