🔬 What is 5-HIAA?

• Full name: 5-Hydroxyindoleacetic acid

• Produced from: The metabolism of serotonin (5-hydroxytryptamine or 5-HT)

• Excreted through: Urine

🧪 Test Name

5-Hydroxyindoleacetic Acid (5-HIAA), Urine Test

This test measures how much 5-HIAA is present in the urine, usually collected over 24 hours.

💡 Purpose of the Test

The test is mainly used to diagnose and monitor carcinoid tumors, which are rare tumors that can produce large amounts of serotonin.

High serotonin levels lead to increased 5-HIAA in the urine.

⚠️ When It’s Ordered

A doctor might order the 5-HIAA test if a patient has symptoms suggestive of carcinoid syndrome, such as:

• Flushing (redness/warmth of skin)

• Diarrhea

• Wheezing or shortness of breath

• Rapid heartbeat

• Abdominal pain or cramping

📊 Normal Range (Typical Reference)

• Adults: 2 to 8 mg/24 hours (varies slightly by lab)

(Note: Always check the specific lab’s reference range.)

📈 High 5-HIAA Levels May Indicate

• Carcinoid tumors (especially of the gastrointestinal tract)

• Metastatic carcinoid cancer

• Rarely, conditions like:

  • Malabsorption syndromes

  • Celiac disease

🍌 Foods and Drugs Affecting Test Results

Certain foods and medications can falsely increase or decrease 5-HIAA levels.
You’ll usually be asked to avoid for 2–3 days before and during collection:

Avoid foods rich in serotonin:

• Bananas 🍌

• Pineapples 🍍

• Tomatoes 🍅

• Plums

• Avocados 🥑

• Eggplant 🍆

• Walnuts

Avoid medications that interfere:

• Cough/cold medicines with guaifenesin

• Acetaminophen (paracetamol)

• Caffeine

• Levodopa

• MAO inhibitors

• Certain antidepressants

🧴 Sample Collection

• Specimen: 24-hour urine

• Container: Acid-preserved collection bottle

• Storage: Keep refrigerated during collection

🧠 Clinical Interpretation