Is Fever a Common Side Effect of Thyroid Cancer Treatment?

Short answer: Fever is not typically expected after thyroid cancer surgery and can signal infection, so you should contact your care team if it happens. ^[1] After radioactive iodine therapy, fever is uncommon, though neck tenderness from thyroiditis and salivary gland issues can occur. ^[2] Certain targeted therapies and immunotherapies can cause non‑infectious fever, which is usually manageable with treatment adjustments and supportive care. ^{[3] [4]}

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Fever After Thyroidectomy (Surgery)

• What’s expected: Pain, temporary hoarseness or voice weakness, and neck discomfort are common after thyroidectomy. Infection is a recognized complication, and fever can be a warning sign. ^{[5] [1]}
• When to act: A postoperative fever should prompt evaluation because it may indicate infection or bleeding-related complications; surgical guidance emphasizes monitoring for infection after thyroidectomy. ^{[1] [6]}

Key point: Fever after surgery is not routine and should be taken seriously, especially if it’s 38.0°C (100.4°F) or higher. ^[1]

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Fever After Radioactive Iodine (RAI, I‑131)

• Typical side effects: Dry mouth, mouth pain, eye inflammation, and changes in taste or smell can occur these depend on dose. Most radioiodine is excreted in urine in the first days, and safety precautions are provided. ^[7]
• Thyroiditis timeline: RAI can provoke thyroiditis around day 3, causing neck tenderness, swelling, sore throat, and pain on swallowing; this is generally managed with analgesics or anti‑inflammatory medicines. ^{[2] [8]}
• Fever: While thyroiditis brings local inflammatory symptoms, fever is not commonly listed as a primary RAI side effect; however, new fever after RAI should be assessed to rule out infection or rare thyroid storm in susceptible cases. ^{[2] [9]}

Key point: After RAI, watch for neck pain and swallowing discomfort; fever isn’t expected and merits clinical review. ^{[2] [7]}

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Fever With Targeted Therapy and Immunotherapy

• BRAF/MEK inhibitors: These agents can cause non‑infectious febrile events (fever syndrome), often within the first 1–3 months; symptoms may include chills, dehydration, dizziness, and fatigue. Educating patients and pausing therapy at onset is recommended, with supportive measures. ^{[10] [11] [3]}
• Immunotherapy (e.g., nivolumab): Fever is among reported adverse reactions and may occur alongside other immune‑related effects; careful monitoring and management are standard. ^[4]

Key point: With targeted and immune therapies, fever can be part of the drug’s side‑effect profile and is often manageable with dose holds, antipyretics, and clinician‑guided adjustments. ^{[3] [10] [4]}

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When Is Fever an Emergency?

• During systemic cancer treatments: A temperature of ≥38.0°C (100.4°F) can be the only sign of infection and may be urgent, especially with treatments that affect immunity. Immediate contact with your doctor is advised. ^{[12] [13]}

Practical rule: If you feel warm, flushed, chilled, or unwell, check your temperature and call your care team at ≥38.0°C (100.4°F). ^{[12] [13]}

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How Fever Is Managed

After Surgery (Thyroidectomy)

• Assessment for infection and wound complications; treatment may include antibiotics if infection is suspected. ^{[1] [6]}
• Do not ignore fever; postoperative instructions highlight contacting the surgeon for fever and increasing pain, redness, or swelling at the incision. ^[14]

After Radioactive Iodine

• Symptom control for thyroiditis: Use pain relievers or anti‑inflammatory medications as advised; monitoring for rare hyperthyroid symptoms is prudent. ^{[2] [8] [9]}
• Report new fever: Evaluate for infection or other causes rather than assuming it’s expected. ^[7]

Targeted Therapy/Immunotherapy

• Hold the drug temporarily at fever onset per protocol and reassess. ^{[10] [3]}
• Supportive care: Antipyretics, fluids, and sometimes prophylactic measures; therapy may resume after resolution, often with adjustments. ^{[10] [11]}

General Safety Tips

• Check temperature promptly if you feel unwell. ^[12]
• Avoid self‑medicating with fever reducers without checking with your provider during or right after cancer treatments, as this can mask important signs. ^[15]
• Call your care team early; infection during cancer therapy can be serious and needs swift evaluation. ^{[13] [12]}

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Quick Reference Table

Treatment phase	Is fever common?	What to do	Typical related issues
Thyroidectomy (post‑op)	No; may indicate infection	Call surgeon if fever ≥38.0°C or wound changes	Pain, hoarseness; monitor for infection
Radioactive iodine (I‑131)	Uncommon	Report fever; manage thyroiditis symptoms	Neck tenderness ~day 3; salivary/tear side effects
Targeted therapy (BRAF/MEK)	Yes, often non‑infectious	Hold drug; supportive care; clinician guidance	Chills, dehydration, dizziness; early months
Immunotherapy	Possible	Monitor; report; manage per protocol	Fever among adverse reactions
Any systemic therapy	Fever can signal infection	Check temp; call at ≥38.0°C	Infection can be serious

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Bottom Line

• After surgery and RAI, fever isn’t expected and should prompt contact with your care team to rule out infection or other complications. ^{[1] [7]}
• With certain drugs, especially BRAF/MEK inhibitors and some immunotherapies, fever can be a known side effect and is usually manageable with temporary treatment holds and supportive care. ^{[10] [3] [4]}
• Always treat a temperature ≥38.0°C (100.4°F) as a reason to call your clinician, as it may be the first sign of infection during cancer treatment. ^{[12] [13]}