1. Individuals with Symptoms of Pellagra: Those showing signs of pellagra, such as dermatitis, diarrhea, and dementia, which can indicate severe niacin deficiency.
2. People with Malabsorption Issues: Individuals with conditions like Crohn’s disease, celiac disease, or chronic alcoholism, which can lead to malabsorption and subsequent nutrient deficiencies.
3. Patients on Long-term Medications: Some medications can interfere with niacin absorption or metabolism.
4. Individuals with Poor Diet: Those with diets lacking in niacin-rich foods (like meat, fish, and whole grains) might benefit from testing, especially if they exhibit deficiency symptoms.
5. Alcoholics: Chronic alcohol abuse can lead to niacin deficiency.

Low levels of nicotinic acid (niacin or vitamin B3) can lead to a deficiency condition known as pellagra. Symptoms of pellagra, or niacin deficiency, include:

1. Dermatitis: Skin becomes rough, red, or inflamed, often in areas exposed to sunlight.
2. Diarrhea: Gastrointestinal disturbances including diarrhea, abdominal pain, and vomiting.
3. Dementia: Cognitive impairment, confusion, disorientation, and memory loss.
4. Depression: Mood changes and depression can occur in early stages.

Improving nicotinic acid (niacin or vitamin B3) levels typically involves dietary changes and, in some cases, supplementation:

1. Dietary Sources: Increase intake of niacin-rich foods such as poultry, beef, fish (like tuna and salmon), whole grains, nuts, and legumes.
2. Balanced Diet: Ensure a well-rounded diet that includes a variety of nutrients, as niacin is part of a healthy dietary pattern.
3. Fortified Foods: Some cereals and breads are fortified with niacin, which can help boost your intake.
4. Supplements: In cases of severe deficiency or for individuals who have trouble getting enough niacin from their diet, supplements might be necessary. This should be done under medical supervision, as high doses of niacin can have side effects.
5. Limit Alcohol Consumption: Alcohol can interfere with the body’s ability to absorb and utilize niacin.
6. Addressing Underlying Health Issues: Conditions that affect nutrient absorption, like Crohn’s disease or chronic alcoholism, should be managed effectively.

Nicotinic acid supplementation can benefit several groups of people:

1. Individuals with Niacin Deficiency: Those showing signs of niacin deficiency, such as symptoms of pellagra (dermatitis, diarrhea, dementia).
2. People with High Cholesterol: High doses of nicotinic acid can be used to treat dyslipidemia, as it can lower LDL (bad) cholesterol and triglycerides and raise HDL (good) cholesterol. However, this should be done under medical supervision due to potential side effects.
3. Those with Poor Dietary Intake: Individuals who have limited access to niacin-rich foods (like vegetarians/vegans or people with certain dietary restrictions) may benefit from supplementation.
4. Individuals with Certain Medical Conditions: Such as Hartnup disease, a rare genetic disorder affecting tryptophan absorption, which can lead to niacin deficiency.
5. People with Malabsorption Issues: Conditions like Crohn’s disease, celiac disease, or chronic alcoholism, which can impair nutrient absorption, might necessitate supplementation.