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Getting ready for thyroid tests: why, the blood tests, the imaging tests, and a nodule
For anyone sent for thyroid blood tests (TSH, T4, T3 or antibodies), a thyroid ultrasound, a thyroid scan, an uptake test, or a needle biopsy of a lump in the neck. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, part of the NIH) says health care professionals use thyroid tests to check how well your thyroid is working and to find the cause of problems such as hyperthyroidism or hypothyroidism. This page passes on, by name, what NIDDK says: what the tests look for; what a high or low TSH can mean, and what else can change the numbers; how the ultrasound, the scan and the uptake test are done; the needle biopsy for a nodule; and getting ready, from iodine to pregnancy and breastfeeding. It builds the words to say and the questions to ask, and prints a card for the fridge with a line for each of your numbers.
Right now
- Trouble breathing, chest pain, or fainting? Call 911 (ours).
- Pregnant or breastfeeding, and booked for a thyroid scan or an uptake test? NIDDK says you should not have either test. Tell them now.
- Told to avoid iodine before a test, and you take a medicine that may contain it? Ask before you stop it. Do not stop or change a prescribed medicine on your own (ours).
- Scared of what the tests may show, or thinking of ending your life? Call or text 988, any hour (ours).
More help
- The thyroid, on this site: Underactive thyroid (hypothyroidism) · Overactive thyroid (hyperthyroidism) · Heart, blood and hormones: find the right page.
- Getting ready: My medicines list · Get ready for your appointment · Rides to care.
- Care and costs: When you need a doctor and can’t pay · Medical bills.
- In a crisis: Help right now (988, 911). All our free tools.
Your heart, blood pressure, blood sugar, thyroid or blood, and not sure this is the right page? The pages on this site for a heart attack or stroke, blood pressure, AFib, heart failure, cholesterol, diabetes and prediabetes, the thyroid, anemia, sickle cell and menopause, on one list.
Another test coming up, or not sure this is the right page? The guides on this site for a colonoscopy, an endoscopy, a GI series, ERCP, a biopsy, a cystoscopy, urodynamic tests, urinary tract imaging, prostate tests, an A1C and thyroid tests, on one list.
Other guides on this site that go with this page
Free to read. We chose these ourselves; no professional did. Each guide was written with AI and has not been reviewed by a professional. They are general information, not advice.
- Thyroid disease and pregnancy: an overactive or underactive thyroid, the medicines, and after the baby: thyroid disease and pregnancy (an overactive or underactive thyroid while pregnant, Graves’ disease or Hashimoto’s disease, or a thyroid that changed after the baby): why the thyroid matters for the baby, the signs, the medicines used in pregnancy and when to stop and call, a higher dose of thyroid medicine, postpartum thyroiditis, breastfeeding, and iodine.
- Prolactinoma: high prolactin, the signs, the tests, and the treatment: prolactinoma and high prolactin (a benign tumor of the pituitary gland, milk from the breasts, periods that changed or stopped, or less interest in sex): the signs, what else raises prolactin, the tests, the medicines, surgery and radiation, and pregnancy.
- Primary hyperparathyroidism: high calcium, the parathyroid glands, the tests, and surgery or watching: primary hyperparathyroidism, when the parathyroid glands make too much hormone and blood calcium runs high: what it is, who gets it, bones and kidney stones, the signs, the causes, the tests, and surgery, watching, medicines and food.
This page and its wording were written with AI (Claude) for Scarlet Beast (our AI policy). No doctor or nurse has reviewed it. The facts were read on October 18, 2026 on NIDDK’s Thyroid Tests page (NIH) and its Spanish version, both last reviewed in May 2017 and saying the same things (where the English page has a slip, “of the most common cause”, we follow the rest of the page: “the most common cause”); the cards also point to NIDDK’s Hypothyroidism, Hyperthyroidism, Hashimoto’s Disease and Graves’ Disease pages. The numbers (an ultrasound of around 30 minutes; avoiding iodine for a week; a scan 30 minutes after an injection or up to 24 hours after swallowing; uptake measurements 4 to 6 hours after and again at 24 hours; a biopsy of less than 30 minutes) are NIDDK’s. Ours: 911 for trouble breathing, chest pain, or fainting; never stopping or changing a prescribed medicine on your own, even one with iodine, without asking; telling them about pregnancy, the pill, steroids or a recent illness before the blood test; writing your numbers on the card; asking what the next test is; asking for the times to come back and planning a ride; that it is fine to ask them to tell you each step; asking who gives the results and when; the card; 988 when it is too much; health centers when money is tight; and the order of the steps. What we left out: brands and doses, normal ranges, the encyclopedia pages NIDDK links for thyroid cancer and oral contraceptives, and the clinical trials section. This page saves nothing and loads no trackers.