What Is Serotonin? Functions, Levels, and Testing Explained

What Is Serotonin?

Serotonin is a chemical substance that acts as both a neurotransmitter and a hormone in the body. It is synthesized primarily in the intestine and brain and is also present in platelets and the central nervous system.

Often referred to as the "good mood hormone," serotonin plays a vital role in regulating mood, sleep, and overall emotional well-being. 

Additionally, it has crucial functions in various bodily systems:

• In the digestive system, serotonin aids in the removal of toxic substances.
• In the circulatory system, it helps with blood clotting and stimulates the muscles of blood vessels.
• It opposes allergic processes and promotes overall immune system health.

Serotonin is a key biomarker in diagnosing specific conditions, especially those related to mood disorders, intestinal health, and certain types of tumors. Its levels in the body can indicate the presence of abnormalities that require medical attention.

When Is Serotonin Testing Recommended?

Serotonin testing is typically ordered to help diagnose conditions involving the digestive system, mood regulation, or other bodily systems influenced by this neurotransmitter. Below are common scenarios where serotonin testing may be prescribed:

• To diagnose abdominal tumors (e.g., in the stomach or intestines).
• When acute intestinal obstruction is suspected.
• To detect vitamin B6 deficiency.
• To assess psycho-emotional states such as mood disorders.
• To evaluate conditions involving the lungs, such as certain types of cancer.

How Is Serotonin Testing Conducted?

Serotonin levels are measured using a blood test, specifically from a sample of venous blood. 

A healthcare provider collects blood from a vein, typically in the arm.

High-performance liquid chromatography (HPLC) is commonly used to analyze serotonin levels in the blood.

Special Preparations for the Test

To ensure accurate results, patients are advised to follow these guidelines:

• Fast for at least 12 hours before the test. Drinking non-carbonated water is allowed.
• Avoid specific foods for 72 hours prior, including:
  • Pineapple
  • Eggplant
  • Cheese
  • Bananas
  • Plums
  • Walnuts
  • Strong tea or coffee
  • Foods with vanillin.
• Refrain from taking certain medications, such as tranquilizers or acetylsalicylic acid-based drugs, unless otherwise advised by your doctor.

What Are the Normal Serotonin Levels?

For adults, normal serotonin levels typically range between 50-200 ng/mL.

Note: The units of measurement and the normal ranges can differ depending on the laboratory and the specific methods used. 

Always consult your healthcare provider for an accurate interpretation of your results.

What Do Abnormal Levels Mean?

Serotonin High Levels

Elevated serotonin levels may indicate several medical conditions or abnormalities. Common causes include:

• Abdominal Neoplasms: Certain tumors in the digestive tract can increase serotonin levels.
• Severe Viral Infections: Intoxication from infections may elevate serotonin as part of the body’s response.
• Bronchial Oat Cell Carcinoma: This rare cancer can lead to elevated serotonin production.
• Medullary Thyroid Cancer: This type of cancer often affects serotonin levels.
• Acute Myocardial Infarction: A heart attack can trigger an increase in serotonin.
• Significant Bleeding: The body’s response to major blood loss may involve serotonin.
• Chemotherapy Side Effects: Certain treatments can lead to higher serotonin levels.
• Cystic Fibrosis Degeneration: Complications of this genetic disorder may elevate serotonin levels.

If you have high serotonin levels, consider these actions:

• Consult with an oncologist if tumors are suspected.
• Follow a balanced diet to support overall health.
• Address any underlying infections with guidance from a physician.
• Work with specialists to manage chronic conditions such as cystic fibrosis.

Serotonin Low Levels

Decreased serotonin levels can indicate a range of health concerns, including:

• Down Syndrome: Individuals with this condition often have lower serotonin levels.
• Parkinson’s Disease: Neurodegenerative conditions can impact serotonin production.
• Parenchymal Liver Disease: Liver dysfunction may affect serotonin metabolism.
• Depression: Low serotonin is commonly associated with mood disorders.
• Vitamin B6 Deficiency: This essential vitamin is needed for serotonin synthesis.
• Phenylketonuria (PKU): This genetic disorder can affect neurotransmitter production.
• Leukemia: Certain blood cancers may lower serotonin levels.

To address low serotonin levels, the following strategies may help:

• Include foods that promote serotonin production, such as those rich in tryptophan (e.g., eggs, turkey, and nuts).
• Engage in regular physical activity to naturally boost mood and serotonin.
• Seek support from a neurologist or mental health specialist for conditions like depression or Parkinson’s.
• Ensure an adequate intake of vitamin B6 through diet or supplementation, as advised by a doctor.

Which Specialist Should You Consult?

Depending on your specific symptoms and test results, you may need to consult one or more of the following specialists:

• Physician: For general health concerns and initial diagnosis.
• Oncologist: If tumors or cancer are suspected.
• Neurologist: For conditions affecting the nervous system, such as Parkinson’s.
• Mental Health Specialist: For mood-related issues like depression.

By understanding serotonin’s role in your body and taking the necessary steps to maintain healthy levels, you can support both your physical and emotional well-being.