Supplements That Cause Flushing
Niacin (vitamin B3) is the primary supplement known to cause flushing, which typically occurs in the face, arms, and chest within 30 minutes of ingestion and can last for about 60 minutes. 1
Niacin (Vitamin B3)
- Flushing is the most common side effect of niacin supplementation, which can occur at doses as low as 30 mg 1
- Flushing symptoms include warmth, redness, itching, and tingling of the skin, especially on the face, neck, chest, and back 2
- The flushing reaction is primarily mediated by prostaglandin D2 and is more common when first starting niacin or when increasing the dose 3
- Niacin-induced flushing tends to decrease in frequency and severity with continued treatment, even with advancing doses 3
- Approximately 5-20% of patients discontinue niacin treatment due to flushing 3
Factors Affecting Niacin-Induced Flushing
- Different niacin formulations have distinct pharmacological profiles that affect the frequency, onset, and duration of flushing 3
- Extended-release niacin formulations can reduce flushing events by up to 76% compared to immediate-release formulations taken three times daily 4
- In clinical studies, approximately 83% of patients taking extended-release niacin reported at least one flushing episode, compared to only 18% of patients taking placebo 4
- Most patients (76%) rate niacin-induced flushing as mild to moderate in intensity 4
Prevention and Management of Niacin-Induced Flushing
- Taking 325 mg of aspirin 30 minutes before niacin dosing can significantly reduce the incidence, intensity, and duration of flushing by 30-40% 5
- Taking niacin with meals or at bedtime with a low-fat snack can minimize flushing 3
- Avoiding exacerbating factors such as alcohol or hot beverages can reduce flushing severity 3
- Slow dose escalation (starting with 0.5-1.0 g/day for 8 weeks before increasing) can improve tolerance 3
Other Supplements That May Cause Flushing
- Nicotinamide mononucleotide (NMN), a precursor to NAD+, does not typically cause flushing unlike nicotinic acid (another form of niacin) 6
- While not specifically mentioned in the evidence, high doses of niacin-containing B-complex vitamins may also cause flushing due to their niacin content
Serious Adverse Effects of Niacin
- Beyond flushing, niacin can cause more serious adverse effects, particularly at higher doses:
- Hepatotoxicity ranging from mild liver enzyme elevation to acute liver failure (typically at doses around 3 g per day) 1
- Gastrointestinal effects including nausea, vomiting, diarrhea, and stomach pain 2
- Hyperglycemia (elevated blood sugar levels) 2
- In rare cases, syncope (fainting) has been reported with sudden increases in niacin dosage 7
Clinical Considerations
- Niacin is sometimes misused by individuals attempting to alter drug test results, although there is no scientific evidence that it can affect test outcomes 8
- The tolerable upper intake level for niacin is 35 mg/day niacin equivalents, with flushing listed as the adverse effect upon which this upper limit is based 1
- For patients requiring niacin for therapeutic purposes, extended-release formulations taken at bedtime with aspirin pretreatment offer the best balance of efficacy and tolerability 3, 5