Carmine (Indigo Carmine)

Also known as: indigo carmine, FD&C Blue No. 2, indigotine, carmine dye, E132, carmine red

Evidence under review. — Not yet rated

Medical dye used in endoscopy and surgery to highlight tissue. Not a dietary supplement.

What it does

Indigo carmine is a synthetic blue dye used medically — not as a dietary supplement. In clinical settings, it is sprayed onto the lining of the colon or stomach during endoscopy to make abnormal...
Evidence quality

Evidence base hasn't been formally rated yet. See research below.
Clinical dose

No established dose

What the Science Says

Indigo carmine is a synthetic blue dye used medically — not as a dietary supplement. In clinical settings, it is sprayed onto the lining of the colon or stomach during endoscopy to make abnormal tissue easier to see, helping doctors detect early cancers and polyps. It is also injected intravenously during surgery to confirm that the ureters are working, where it turns urine blue within minutes and clears from the body within about 2 hours.

What It Doesn't Do

Not a supplement you take for health benefits. No evidence it improves digestion, gut health, or any wellness outcome. Not a probiotic, prebiotic, or detox agent. The 518 registered supplement products likely use carmine (cochineal red dye) as a colorant — not as an active ingredient with any therapeutic effect.

Evidence-Based Benefits

Helps doctors spot abnormal tissue in the colon and stomach when sprayed during endoscopy.

Moderate Evidence

Effective at: 0.1–0.4% solution, 20–40 mL sprayed topically

Supporting studies (click to view on PubMed):

PMID 40079452 PMID 33228549 PMID 42401450 PMID 42109620

Turns urine blue within minutes after IV injection, confirming the ureters are working during surgery.

Moderate Evidence

Effective at: 2.5–5.0 mL IV injection

Supporting studies (click to view on PubMed):

PMID 42149631

Absorption & Bioavailability

Rapid when injected IV — plasma half-life ~12 minutes, cleared from blood within 2 hours. Primarily excreted in urine. When used as a food colorant, absorption data from the provided studies is limited.

Red Flags to Watch For

Carmine (cochineal red) and indigo carmine are two different substances — products may use either as a colorant with no therapeutic intent
Lab study suggests indigo carmine may promote abnormal protein aggregation (amyloid fibrillation) in milk proteins under acidic conditions — food safety implications unclear
No clinical evidence supports taking carmine or indigo carmine orally as a supplement for any health benefit
Presence in 518 supplement products almost certainly reflects use as a coloring agent, not an active ingredient — consumers may not realize they are ingesting a synthetic dye

Frequently Asked Questions

What does Carmine (Indigo Carmine) do?

Medical dye used in endoscopy and surgery to highlight tissue. Not a dietary supplement.

What is the effective dose of Carmine (Indigo Carmine)?

No established dose

Is Carmine (Indigo Carmine) safe?

Carmine (cochineal red) and indigo carmine are two different substances — products may use either as a colorant with no therapeutic intent

What doesn't Carmine (Indigo Carmine) do?

Not a supplement you take for health benefits.

Research Sources

PubMed
NIH DSLD

This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-07-05