Thyroid uptake and scan (thyroid nuclear test) Diagnostic Imaging

A thyroid uptake and scan is a nuclear medicine test that shows how your thyroid looks and how it uses iodine.

Thyroid uptake and scan (thyroid nuclear test) procedure illustration

Overview

A thyroid uptake and scan is a nuclear medicine test that shows how your thyroid looks and how it uses iodine. A small amount of radioactive material, often iodine-123 or technetium-99m, is given by pill or injection. A special camera then takes pictures, and the uptake measurement shows how much iodine the thyroid absorbs. This test helps explain the cause of an overactive or enlarged thyroid and evaluates nodules. It can help tell the difference between conditions like Graves disease and thyroiditis, and it can show if a nodule is “hot” (making extra hormone) or “cold” (not active).

Overview Preparation Clinical Info Recovery FAQ References

Also known as: Thyroid scan, RAIU test, Thyroid scintigraphy

Recovery
Same day
Return to Work
Same day

Preparation & Next Steps

Everything you need to know before and after your procedure

Before Care

  • Plan for timed visits; many centers do images and uptake measurements over the same day and the next day.
  • Bring a current list of all medicines and supplements, including iodine, kelp, multivitamins, and biotin.
  • Share any recent CT scans or other tests that used iodinated contrast dye, as this can affect results.
  • Inform the imaging team about pregnancy, trying to conceive, or breastfeeding.
  • Follow any fasting instructions provided for the tracer capsule or injection.
  • You may be asked to pause certain medicines or supplements that interfere with the test; follow the imaging center’s instructions.
  • Avoid high-iodine foods or supplements if the imaging team requests it.
  • Remove necklaces or metal near the neck and wear a loose, open-neck shirt.
  • Bring recent thyroid labs and any prior thyroid ultrasound or biopsy reports if available.
  • Arrive early to review safety questions and consent forms.

After Care

  • Most people return to normal activities right away after imaging.
  • Drink fluids as allowed to help your body clear the tracer unless you were told otherwise.
  • You may receive guidance about limiting close contact with infants and pregnant individuals for a short time after the test.
  • If any medicines were held, the imaging team or your ordering clinician will tell you when to restart them.
  • Watch the injection site for redness, warmth, or swelling and contact a clinician if concerns arise.
  • Mild nausea or metallic taste can occur and usually passes quickly; report severe or persistent symptoms.
  • If breastfeeding, follow specific instructions about pumping and discarding milk if advised.
  • Expect results to be shared by the imaging center or referring clinician, often within a few days.
  • Keep a record of the tracer and dose you received in case you have future imaging.

Clinical Information

Important medical details about this procedure

Indications

  • Evaluating hyperthyroidism or suspected overactive thyroid
  • Differentiating Graves disease from thyroiditis
  • Assessing thyroid nodules (hot vs cold)
  • Investigating goiter (enlarged thyroid) or abnormal thyroid function tests
  • Locating thyroid tissue in unusual positions (ectopic thyroid)

Alternatives

  • Thyroid blood tests (TSH, T3, T4)
  • Thyroid antibody tests
  • Thyroid ultrasound with Doppler
  • Fine-needle aspiration biopsy for suspicious nodules
  • CT or MRI in selected cases when anatomy, not function, is the main question

Risks

  • Low radiation exposure from the tracer
  • Very rare allergic or adverse reactions to the tracer
  • Minor discomfort from an injection or swallowing a capsule
  • Interference from recent iodine, contrast dye, or medicines may affect results
  • Potential risk to a fetus or nursing infant from radiation exposure

Contraindications

  • Pregnancy
  • Breastfeeding unless specific precautions are arranged
  • Recent iodinated contrast dye exposure
  • Use of high-iodine substances or certain medicines that interfere (for example, amiodarone)
  • Inability to follow preparation or timing requirements

Recovery Timeline

What to expect during your recovery

There is no medical recovery period for most thyroid uptake and scan exams. People usually resume normal activities immediately after each imaging session.

Typical Range

Same day

Return to Work

Same day

Recovery Milestones

Day 0

Resume normal daily activities

Day 0–1

Drink fluids regularly unless told otherwise

Day 0–1

Follow any short-term contact precautions provided by the imaging team

Day 0–2

Review results and next steps with the ordering clinician

Frequently Asked Questions

Common questions and expert answers about this procedure

What is the difference between the uptake and the scan?

The uptake measures how much radioactive iodine the thyroid absorbs over time. The scan takes pictures that show the thyroid’s size, shape, location, and areas that are overactive or underactive.

Which tracer is used for this test?

Common tracers are iodine-123 taken by mouth or technetium-99m given by injection. Your imaging center selects the tracer based on the clinical question and local practice.

How long does the test take?

Timing varies. Many centers do an initial visit for the tracer and early measurements, then imaging later the same day or the next day. Plan for several short sessions within 24 hours.

Will the radiation dose be high?

The dose for diagnostic thyroid uptake and scan is low and kept as small as reasonably achievable while still getting clear images.

Can I have this test if I am pregnant or breastfeeding?

Pregnancy is generally a contraindication. Breastfeeding often requires special precautions or temporary interruption, depending on the tracer. The imaging team will review options.

Do I need to stop any medicines or supplements?

Some medicines and iodine-containing products can interfere with results. The imaging center may give specific instructions about holding or timing these before the study.

Can this test tell if a thyroid nodule is cancer?

The scan shows if a nodule is functioning (“hot”) or not (“cold”). A cold nodule is more likely to need ultrasound assessment and possibly a biopsy to check for cancer.

Will I be radioactive after the test?

A small amount of tracer remains in your body for a short time and is cleared mainly through urine. You may receive brief safety instructions after the study.