What it's used for
Ondansetron is used to prevent nausea and vomiting associated with highly or moderately emetogenic cancer chemotherapy, radiation therapy, and postoperative nausea and vomiting.
Source: U.S. FDA-approved prescribing information (openFDA).
Typical dosing
Dosage regimens vary for adult and pediatric patients depending on the indication, and patients with severe hepatic impairment should not exceed a total daily dose of 8 mg.
Dosing shown here is the general FDA-labeled range. Your prescribing clinician determines the exact dose, form, and schedule for you — this is not a substitute for medical advice.
What it looks like
Illustrative only — appearance varies by manufacturer and strength. Photo credit: NLM.
Common side effects
The most common adverse reactions in adults for chemotherapy prevention include headache, fatigue, and constipation.
Covered strengths on the Tab $0 list
Covered at $0 with an active Tab membership when filled at a participating pharmacy nationwide or through mail order. A licensed clinician must prescribe the medication.
Related medications
Other everything else medications covered at $0 with an active Tab membership.
Ondansetron cost without insurance
Cash prices for Ondansetron without insurance vary widely by pharmacy, strength and quantity — the same prescription can cost very different amounts at two pharmacies in the same town. That is the problem a membership solves.
Ondansetron is on Tab's covered $0 generic list. With an active Tab membership, every covered strength is $0 — not a percentage off, not a coupon that changes month to month — at participating pharmacies nationwide or through mail order. You do not need insurance, and Tab works whether or not you have a health plan.
Tab is a membership, not insurance. Covered medications require a prescription from a licensed clinician.
Ondansetron dosage and administration
See full prescribing information for the recommended dosage in adults and pediatrics (2) Patients with severe hepatic impairment: do not exceed a total daily dose of 8 mg ( 2.2 , 8.6 ) 2.1 Dosage The recommended dosage regimens for adult and pediatric patients are described in Table 1 and Table 2, respectively. Corresponding doses of ondansetron tablets may be used interchangeably.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Your prescribing clinician decides the exact dose, form and schedule for you — this is not medical advice.
Ondansetron side effects
The following clinically significant adverse reactions are described elsewhere in the labeling: Hypersensitivity Reactions [see Warnings and Precautions ( 5.1 )] QT Prolongation [see Warnings and Precautions (5.2 )] Serotonin Syndrome [see Warnings and Precautions ( 5.3 )] Myocardial Ischemia [see Warnings and Precautions ( 5.4 )] Masking of Progressive Ileus and Gastric Distension [see Warnings and Precautions [see Warnings and Precautions ( 5.5 )] The most common adverse reactions in adults for the: prevention of chemotherapy-induced (≥5%) are: headache, malaise/fatigue, constipation, diarrhea ( 6.1 ) prevention of radiation-induced nausea and vomiting (≥2%) are: headache, constipation, and diarrhea ( 6.1 ) prevention of postoperative nausea and vomiting (≥9%) are: headache and hypoxia ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Dr.
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. This is not a complete list. Report side effects to your clinician, and seek care for anything severe or unexpected.
Ondansetron drug interactions
7.1 Serotonergic Drugs Serotonin syndrome (including altered mental status, autonomic instability, and neuromuscular symptoms) has been described following the concomitant use of 5-HT 3 receptor antagonists and other serotonergic drugs, including SSRIs and SNRIs. Monitor for the emergence of serotonin syndrome. If symptoms occur, discontinue ondansetron and initiate supportive treatment [see Warnings and Precautions ( 5.3) ]. 7.2 Drugs Affecting Cytochrome P-450 Enzymes Ondansetron does not itself appear to induce or inhibit the cytochrome P-450 drug-metabolizing enzyme system of the liver [see Clinical Pharmacology (12.3)].
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Tell your clinician and pharmacist about every medication, supplement and over-the-counter product you take.
Who should not take ondansetron
Ondansetron is contraindicated in patients: known to have hypersensitivity (e.g., anaphylaxis) to ondansetron or any of the components of the formulation [see Adverse Reactions (6.2) ] receiving concomitant apomorphine due to the risk of profound hypotension and loss of consciousness Patients known to have hypersensitivity (e.g., anaphylaxis) to ondansetron or any components of the formulation. (4) Concomitant use of apomorphine (4)
Excerpt from the FDA-approved prescribing information (openFDA), retrieved 2026-09-15. Whether this medication is appropriate for you is a clinical decision made by your prescribing clinician.
Common questions
Is ondansetron covered at $0 with Tab?
Yes. Ondansetron is on Tab's covered $0 generic list — every covered strength is $0 with an active membership, at participating pharmacies nationwide or by mail order.
Do I need insurance to get ondansetron through Tab?
No. Tab is a membership, not insurance. Covered medications are $0 with an active membership whether or not you have a health plan.
How do I get an ondansetron prescription with Tab?
Book a video visit with a licensed Tab clinician (unlimited visits are included with membership). If it's clinically appropriate, they send the prescription to your chosen participating pharmacy or by mail order.
How much does ondansetron cost without insurance?
Without insurance, retail cash prices for ondansetron vary by pharmacy, strength and quantity. Ondansetron is on Tab's covered $0 generic list, so every covered strength is $0 with an active Tab membership at participating pharmacies nationwide or by mail order.
What is the cheapest way to get ondansetron?
For medications on Tab's covered list, a Tab membership is the cheapest route: covered strengths of ondansetron are $0 with an active membership, and unlimited video visits with a licensed clinician are included, so the visit that produces the prescription is covered too.
What is the usual dose of ondansetron?
See full prescribing information for the recommended dosage in adults and pediatrics (2) Patients with severe hepatic impairment: do not exceed a total daily dose of 8 mg ( 2.2 , 8.6 ) 2.1 Dosage The recommended dosage regimens for adult and pediatric patients are described in Table 1 and Table 2, respectively. Corresponding doses of ondansetron tablets may be used interchangeably. (FDA-approved label, retrieved 2026-09-15. Your clinician sets your dose.)
What are the side effects of ondansetron?
The following clinically significant adverse reactions are described elsewhere in the labeling: Hypersensitivity Reactions [see Warnings and Precautions ( 5.1 )] QT Prolongation [see Warnings and Precautions (5.2 )] Serotonin Syndrome [see Warnings and Precautions ( 5.3 )] Myocardial Ischemia [see Warnings and Precautions ( 5.4 )] Masking of Progressive Ileus and Gastric Distension [see Warnings and Precautions [see Warnings and Precautions ( 5.5 )] The most common adverse reactions in adults for the: prevention of chemotherapy-induced (≥5%) are: headache, malaise/fatigue, constipation, diarrhea ( 6.1 ) prevention of radiation-induced nausea and vomiting (≥2%) are: headache, constipation, and diarrhea ( 6.1 ) prevention of postoperative nausea and vomiting (≥9%) are: headache and hypoxia ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Dr. (FDA-approved label, retrieved 2026-09-15.)
What interacts with ondansetron?
7.1 Serotonergic Drugs Serotonin syndrome (including altered mental status, autonomic instability, and neuromuscular symptoms) has been described following the concomitant use of 5-HT 3 receptor antagonists and other serotonergic drugs, including SSRIs and SNRIs. Monitor for the emergence of serotonin syndrome. (FDA-approved label, retrieved 2026-09-15. Tell your clinician about every medication and supplement you take.)
Ondansetron is $0 on the covered list
Members pay $0 for covered generics at participating pharmacies nationwide or by mail order — plus unlimited virtual primary care, urgent care and dermatology visits. No insurance needed.
Solo $49/mo · Family $119/mo for up to 4 people · Family+ $149/mo for up to 8
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