Your thyroid: TSH, Hashimoto's and levothyroxine — Reclaim Power Telehealth patient library

Your Thyroid: TSH, Hashimoto's, and Taking Levothyroxine Right

September 20, 2026

Hormones · Metabolism

A small gland that sets the pace for your whole body. Here is how we check it, and what the numbers can and cannot explain.

Written for my patients. If you are not one, read "call me" as "call your own clinician", and take the questions here to them.

What it does

Your thyroid makes hormones that set your body's pace: energy, heart rate, body temperature, digestion, and how fast you burn fuel. Your brain's pituitary gland keeps it in check by sending a signal called TSH. When thyroid hormone runs low, TSH goes up to push harder. That is why a high TSH usually means an underactive thyroid.

Underactive or overactive

UnderactiveHypothyroidism. Fatigue, feeling cold, constipation, dry skin, hair thinning, heavy periods, low mood, slow thinking, modest weight gain. In the U.S. the most common cause is Hashimoto's, an autoimmune condition.

OveractiveHyperthyroidism. Racing heart, anxiety, tremor, heat intolerance, weight loss, diarrhea, trouble sleeping. Needs prompt evaluation.

Many of these symptoms overlap with perimenopause, poor sleep, low iron, and depression. A normal thyroid test is useful, because it tells us to look elsewhere.

The labs

Test	What it tells us
TSH	The best single screening test. Normal is roughly 0.4 to 4.5 in most labs.
Free T4	The main hormone your thyroid makes. Checked when TSH is off, or to adjust treatment.
TPO antibodies	Show whether Hashimoto's is the cause. Positive antibodies with normal TSH mean we watch your levels over time.
Free T3, reverse T3	Rarely change treatment decisions. Thyroid experts do not recommend reverse T3 for routine care, so I do not use it to guide dosing.

Treatment

Well established

LevothyroxineReplaces the T4 hormone. Standard, inexpensive, and effective for most people. We adjust your dose by TSH, usually checked 6 to 8 weeks after any change.

Mild changes may not need pillsIn a trial of adults 65 and older with slightly high TSH and normal T4, levothyroxine did not improve symptoms or energy. We treat based on your numbers, age, symptoms, and plans for pregnancy.

Case by case

Adding T3Some people still feel unwell on levothyroxine alone. Thyroid societies say a trial of added T3 is reasonable for some of them. We can talk about it.

Selenium, gluten-freeSelenium lowers thyroid antibodies in some studies, but it has not been shown to change how people feel or how the disease progresses. A gluten-free diet helps if you also have celiac disease.

Taking levothyroxine the right way

Take it with water on an empty stomach, 30 to 60 minutes before breakfast or coffee. Or at bedtime, at least 3 hours after eating. Pick one and be consistent.
Keep calcium, iron, magnesium, and antacids at least 4 hours away from it. They block absorption.
Stay on the same brand or maker when you can. Switching can change your levels a little.
Stop biotin 2 to 3 days before thyroid labs. It can make results look falsely abnormal.
Tell me right away if you become pregnant. Your dose usually needs to go up.

Call me if

Your heart is racing or skipping, you feel shaky or anxious, or you are losing weight without trying while on thyroid medicine; your dose may be too high. Also call for a new lump in your neck, trouble swallowing, or hoarseness that does not go away.

I wrote this for my patients, and it reads the same for everyone: general information, not a plan. If you would like your own numbers read against your own story, that is what a Lab Second Look is for. If you are not sure where to start, the free intro call is fifteen minutes.

A note on how to use this. General information for my patients, not individualized advice.

Jonklaas J et al. Guidelines for the treatment of hypothyroidism: American Thyroid Association. Thyroid 2014;24(12):1670–751.
Stott DJ et al. Thyroid hormone therapy for older adults with subclinical hypothyroidism (TRUST). N Engl J Med 2017;376(26):2534–44.
Jonklaas J et al. Evidence-based use of levothyroxine/liothyronine combinations: ATA/ETA/BTA consensus. Thyroid 2021;31(2):156–82.
U.S. Food and Drug Administration. Biotin interference with lab tests: safety communication (updated 2019).

Trang Ca Laube, FNP-BC, FMACP · Reclaim Power Telehealth · Updated September 2026

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Trang Ca Laube, FNP-BC, FMACP

Board-certified Family Nurse Practitioner and Functional Medicine Certified Practitioner. Founder of Reclaim Power Telehealth, seeing adults in Indiana, Colorado, Utah, Washington and Arizona. Author of The Safety Switch. These handouts are general information written for my patients, not individualized advice.

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