If you’ve been diagnosed with hypothyroidism and are still not feeling like yourself—even though your lab work shows “normal” thyroid levels—you may have wondered: Should I be taking T3?
It’s a common question, and for good reason. T3 (triiodothyronine) is the active form of thyroid hormone, and it plays a key role in metabolism, energy, mood, body temperature regulation, and more. But just because it’s powerful doesn’t mean it’s the right solution for everyone.
According to Dr. Lindsey VanDyke, DO, FACOI, FEAA, board-certified endocrinologist and founder of the Advanced Institute for Diabetes & Endocrinology in Mansfield, TX, the decision to start T3 therapy should always be highly personalized.
“A lot of people ask, should I be on T3? And the answer is—maybe, sometimes,” says Dr. VanDyke.
So how do you know if you’re one of those “sometimes”? Let’s explore.
Understanding T3 and T4
Your thyroid produces several types of hormones, but we focus on two of them: T4 (thyroxine) and T3 (triiodothyronine). Most hypothyroid patients are treated with T4 replacement, typically in the form of levothyroxine. The molecular structure is identical to the T4 you make on your own, and this medication has a long half-life, making it ideal for steady, once-daily dosing.
T4 is converted into T3 in the body, which is the form your cells actually use. However, some people may have trouble converting T4 into T3 efficiently. In those cases, it might make sense to consider supplementing with T3 directly—but not before thoroughly evaluating all other factors.
Don’t rush into T3: why timing matters
Thyroid hormone levels take time to stabilize. Unlike fast-acting medications, levothyroxine can take 6 to 8 weeks to fully reflect in your lab work and symptoms.
“There’s a lot of impatience when treating hypothyroidism,” explains Dr. VanDyke. “But dialing in the right dose is a process that takes weeks to months.”
Making rapid changes—especially without stabilizing T4 levels first—can cause more harm than good. In fact, certain conditions can temporarily affect how your body processes thyroid hormone, including:
- Recent illness or infection
- Pregnancy
- Medications that either block or enhance thyroid hormone metabolism (e.g., steroids, oral contraceptives, antacids)
- Stress, dietary changes, or shifts in body weight
These variables must be accounted for before making any adjustment to your thyroid medication regimen.
Before adding T3, get your T4 right
One of the most important steps before considering T3 is ensuring your T4 dose is fully optimized. If your T4 isn’t stable, adding T3 may not yield any benefit and could even make you feel worse.
“We have to make sure that the T4 portion of your treatment is completely optimal and stable before we even think about T3,” says Dr. VanDyke.
Stability means:
- Consistent lab results over time
- No dose changes in the past several weeks
- You’re taking your medication correctly and at the same time daily
- Your symptoms are not due to another underlying condition
Only after these criteria are met can a thoughtful discussion about T3 supplementation begin.
Who might benefit from T3 therapy?
Not every patient with hypothyroidism needs T3, but there are some who may genuinely benefit. This group often includes individuals who:
- Have stable T4 levels and appropriate lab values
- Are still experiencing persistent fatigue, brain fog, or mood changes
- Notice a drop in energy or alertness in the late afternoon
- Have exhausted other causes of these symptoms, such as anemia, vitamin deficiencies, or poor sleep
In some cases, a low dose of T3 may help smooth out these energy dips or cognitive symptoms. This is typically added on top of the existing T4 regimen in a carefully monitored manner.
“Sometimes we give them a small taste of T3 and see if they respond better,” says Dr. VanDyke. “Not everyone will, but for some, it makes a meaningful difference.”
Why T3 therapy requires close supervision
Unlike T4, which has a long and steady release, T3 acts quickly and peaks within a few hours of taking it. This can lead to side effects like palpitations, anxiety, jitteriness, or insomnia—especially if the dose is too high or not timed properly.
This is why T3 should only be considered under the care of a specialist who understands the complexities of hormone metabolism. Self-adjusting your dose, switching to compounded T3 without supervision, or using unregulated supplements can lead to inconsistent hormone levels and serious health consequences.
The bottom line
If you’re wondering whether T3 could be the missing link in your thyroid treatment, the answer depends on your individual health picture. While it’s not necessary—or appropriate—for everyone, T3 can be helpful in select patients whose symptoms persist despite stable T4 therapy.
The key is patience, thorough evaluation, and working with a provider who doesn’t just look at labs—but listens to your symptoms and takes the time to understand your whole story.
“It’s a very individualized process,” says Dr. VanDyke. “We’re not just treating numbers—we’re treating people.”
About Dr. Lindsey VanDyke & Advanced Institute
Dr. Lindsey VanDyke, DO, FACOI, FEAA, is a board-certified endocrinologist and founder and CEO of the Advanced Institute for Diabetes & Endocrinology in Mansfield, TX. She is a recognized leader in thyroid disease, diabetes care, obesity management, and hormone health, and was among the first endocrinologists in the U.S. to offer non-surgical radiofrequency ablation (RFA) for thyroid nodules.
With a patient-first, integrative approach, Dr. VanDyke provides care that’s evidence-based, accessible, and built around what matters most—you.
Visit www.aidendo.com to learn more or schedule a consultation.
Watch more insights on hormone health at YouTube.com/@DrLindseyVanDyke
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