Regulatory neurotransmitter found in GI tract, blood platelets, and nervous system, with many functions including mood, sleep, appetite, and blood clotting.Encyclopedia Entry for Serotonin :Serotonin blood test. A blood sample is needed.No special preparation is needed.When the needle is inserted to draw blood, some people feel slight pain. Others feel a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.Serotonin is a chemical produced by nerve cells. This test may be done to diagnose carcinoid syndrome. Carcinoid syndrome is a group of symptoms associated with carcinoid tumors. These are tumors of the small intestine, colon, appendix, and bronchial tubes in the lungs. People with carcinoid syndrome often have high levels of serotonin in the blood.The normal range is 50 to 200 ng/mL (0.28 to 1.14 mol/L). Note: Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your health care provider about the meaning of your specific test results.A higher-than-normal level may indicate carcinoid syndrome.There is very little risk in having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others. Other risks may include: Excessive bleeding Fainting or feeling lightheaded Hematoma (blood accumulating under the skin) Infection (a slight risk any time the skin is broken).5-HT level; 5-hydroxytryptamine level; Serotonin test.Blood test Blood test.Chernecky CC, Berger BJ. Serotonin (5-hydroxytryptamine) - serum or blood.Encyclopedia Entry for Serotonin :Serotonin syndrome. SS most often occurs when two medicines that affect the body's level of serotonin are taken together at the same time. The medicines cause too much serotonin to be released or to remain in the brain area. For example, you can develop this syndrome if you take migraine medicines called triptans together with antidepressants called selective serotonin reuptake inhibitors (SSRIs), and selective serotonin/norepinephrine reuptake inhibitors (SSNRIs). Common SSRIs include citalopram (Celexa), sertraline (Zoloft), fluoxetine (Prozac), paroxetine (Paxil), and escitalopram (Lexapro). SSNRIs include duloxetine (Cymbalta) and venlafaxine (Effexor). Common triptans include sumatriptan (Imitrex), zolmitriptan (Zomig), frovatriptan (Frova), rizatriptan (Maxalt), almotriptan (Axert), naratriptan (Amerge), and eletriptan (Relpax). If you take these medicines, be sure to read the warning on the packaging. It tells you about the potential risk of serotonin syndrome. However, do not stop taking your medicine. Talk to your doctor about your concerns first. SS is more likely to occur on starting or increasing the medicine. Older antidepressants called monoamine oxidase inhibitors (MAOIs) can also cause SS with the medicines described above, as well as meperidine (Demerol, a painkiller) or dextromethorphan (cough medicine). Drugs of abuse, such as ecstasy, LSD , cocaine , and amphetamines have also been associated with SS.Symptoms occur within minutes to hours, and may include: Agitation or restlessness Abnormal eye movements Diarrhea Fast heartbeat and high blood pressure Hallucinations Increased body temperature Loss of coordination Nausea and vomiting Overactive reflexes Rapid changes in blood pressure.The diagnosis is usually made by asking the person questions about medical history, including the types of drugs. To be diagnosed with SS, the person must have been taking a drug that changes the body's serotonin level (serotonergic drug) and have at least three of the following signs or symptoms: Agitation Abnormal eye movements (ocular clonus, this is a key finding in establishing a diagnosis of SS) Diarrhea Heavy sweating not due to activity Fever Mental status changes, such as confusion or hypomania Muscle spasms (myoclonus) Overactive reflexes ( hyperreflexia ) Shivering Tremor Uncoordinated movements (ataxia) SS is not diagnosed until all other possible causes have been ruled out. This may include infections, intoxication, metabolic and hormone problems, and drug or alcohol withdrawal. Some symptoms of SS can mimic those due to an overdose of cocaine, lithium, or an MAOI. If a person has just started taking or increased the dosage of a tranquilizer (neuroleptic drug), other conditions such as neuroleptic malignant syndrome (NMS) will be considered. Tests may include: Blood cultures (to check for infection) Complete blood count (CBC) CT scan of the brain Drug (toxicology) and alcohol screen Electrolyte levels Electrocardiogram (ECG) Kidney and liver function tests Thyroid function tests.People with SS will likely stay in the hospital for at least 24 hours for close observation. Treatment may include: Benzodiazepine medicines, such as diazepam (Valium) or lorazepam (Ativan) to decrease agitation, seizure-like movements, and muscle stiffness Cyproheptadine (Periactin), a drug that blocks serotonin production Intravenous (through the vein) fluids Withdrawal of medicines that caused the syndrome In life-threatening cases, medicines that keep the muscles still (paralyze them), and a temporary breathing tube and breathing machine will be needed to prevent further muscle damage.People may get slowly worse and can become severely ill if not quickly treated. Untreated, SS can be deadly. With treatment, symptoms usually go away in less than 24 hours.Uncontrolled muscle spasms can cause severe muscle breakdown. The products produced when the muscles break down are released into the blood and eventually go through the kidneys. This can cause severe kidney damage if SS isn't recognized and treated properly.Call your health care provider right away if you have symptoms of serotonin syndrome.Always tell your providers which medicines you take. People who take triptans with SSRIs or SSNRIs should be closely followed, especially right after starting a medicine or increasing its dosage.Hyperserotonemia; Serotonergic syndrome; Serotonin toxicity; SSRI - serotonin syndrome; MAO - serotonin syndrome.Fricchione GL, Beach SR, Huffman JC, Bush G, Stern TA. Life-threatening conditions in psychiatry: catatonia, neuroleptic malignant syndrome, and serotonin syndrome.