Niacin deficiency
Symptoms, at-risk groups, and clinical context for niacin deficiency. Sourced from NIH Office of Dietary Supplements and StatPearls.
Severe niacin (vitamin B3) deficiency causes pellagra — historically known as the disease of the 'four Ds': dermatitis, diarrhea, dementia, and (if untreated) death. Pellagra is now extremely rare in the US thanks to grain fortification, but mild inadequacy persists in some populations, and pellagra still appears in alcoholics, people with malabsorption, and certain medical settings.
Common symptoms
- Pigmented, scaly rash on sun-exposed skin (face, neck 'Casal's necklace', arms, hands)
- Bright red, swollen tongue and mouth sores
- Diarrhea, abdominal pain, vomiting
- Fatigue and weakness
- Headache and apathy
- Memory loss, confusion, or dementia (in severe cases)
- Depression, anxiety, irritability
- Loss of appetite
At-risk groups
- People with alcohol use disorder (most common cause of pellagra in developed countries)
- People in resource-limited settings with corn/maize-dominant diets
- People with anorexia or severely restricted diets
- People with carcinoid syndrome (tryptophan diverted to serotonin synthesis)
- People taking isoniazid for tuberculosis (interferes with niacin synthesis)
- People with Hartnup disease (rare hereditary tryptophan absorption disorder)
- People with malabsorption conditions (Crohn's, celiac, post-bariatric surgery)
- Long-term users of certain medications (5-fluorouracil, pyrazinamide)
When to see a doctor: A symmetric rash on sun-exposed skin combined with diarrhea and cognitive changes (the classic 'three Ds') in any at-risk person warrants urgent medical evaluation. Pellagra is rapidly reversible with treatment but fatal if ignored.
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Related deficiencies
Nutrients with overlapping symptoms — useful when investigating an unclear clinical picture.