Optimizing your T3 is probably the single most important thing you can do as a thyroid patient.
And when it comes to increasing your T3 status, you have two options:
#1. T3 support supplements.
#2. T3 medications.
Choosing the right option may feel difficult, but it doesn’t have to be.
Because the reality is that for most thyroid patients, the best route is to use both at the same time.
Here’s why:
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What You Need To Know About T3
T3, also known as triiodothyronine, is the most powerful and active thyroid hormone.
It’s responsible for regulating your metabolism (1) (more than any other thyroid hormone, except T2), regulating energy levels (2), and overall thyroid balance (3).
Unlike T4 thyroid hormone, which is found in levothyroxine, T3 does everything that you want your thyroid to do:
Grow your hair, help you lose weight, speed up your thoughts, rev up your metabolism, improve your energy, and so on.
Most thyroid patients don’t have enough T3 in their body, which is why they are constantly trying to get more of it.
And why both T3 medications and T3 supplements are so popular.
Both options work, but they differ in how they impact your body, their relative strength, and, as a result, their side effects.
Differences Between T3 Medications & T3 Supplements
When thinking about which one you should use, you need to understand a couple of important differences.
T3 Supplements:
- These are available over the counter.
- They contain research-backed ingredients that help your body naturally create more T3 on its own.
- They work by supporting the conversion of T4 into T3 by activating deiodinase enzymes in your body, by providing your thyroid with the building blocks it needs to create thyroid hormone, and by supporting tissues involved in recycling T3.
- They are milder compared to T3 medications, but still very effective.
- Have far fewer side effects relative to T3 medications.
T3 Medications:
- These are available only with a prescription.
- They contain pure, active T3 thyroid hormone.
- They provide you with a direct source of T3 instead of helping your body produce it.
- They are stronger than T3 supplements so they provide more immediate effects (both positive and negative).
- They are FDA-approved for thyroid disorders (4).
- They have a much higher potential for side effects due to their strength.
- And they are much more difficult to obtain.
T3 Supplement Side Effects
Probably the biggest difference between them is their potential to cause side effects.
I’ve been helping thyroid patients for years, and over that time, well over 20,000 thyroid patients have used my T3 support supplements.
Based on that data, here are some of the most common side effects that occur when using these natural options:
- Mild Stimulation: Most thyroid patients experience a mild boost in energy without jitters or nervous energy, but some people may experience mild overstimulation which is uncomfortable.
- Digestive Upset: Some people report nausea or stomach discomfort when taking T3 supplements. This is most likely due to the natural botanicals and other compounds that are needed to support thyroid function. This particular side effect can often be managed by taking your supplement with food or by cutting back on your dose.
- Sleep disturbances (mild): Rarely, some people experience issues relating to sleep when supporting their T3 status. This generally occurs when the supplement is taken later in the day (instead of first thing in the morning) and can often be solved by taking your dose right when you wake up. Some people are just very sensitive to changes in their T3 status, though, and may need to ultimately stop taking it. Be very mindful of your sleep and your thyroid because anything that makes you sleep less will also cause negative effects on both T4 and T3 levels.
- Heart Palpitations: Heart palpitations are rare when using T3 supplements, but some people do experience them. This particular side effect feels scarier than it really is, though, because the reality is that heart palpitations are almost never dangerous. If you do experience this problem, try to reduce your dose and it should improve.
- No benefit at all: Believe it or not, the most common negative side effect is no side effect at all! Based on my experience, negative side effects only occur in about 1-5% of thyroid patients who use T3 supplements. About 15% or so will experience no benefit at all and the remaining 80% will see a varying degree of improvement. But when you look at this breakdown, it’s easy to see that the no improvement category is much larger than the negative side effect. For those who don’t see any improvement, this can usually be fixed by swapping to another supplement or by making changes to their expectations (T3 supplements, while powerful, will not completely solve your thyroid problem by themselves).
This might sound like a lot, but, in general, they are very well tolerated.

T3 Medication Side Effects
T3 is only found in certain thyroid medications, like Cytomel and liothyronine (and NDT formulations).
Because of their raw power, they are much more likely to cause side effects.
Some of the more mild and common side effects include:
- Heart palpitations: This is a VERY common side effect with T3 medications and it occurs because T3 has a direct impact on cardiac myocytes. Because your heart cells interact directly with T3 thyroid hormone (5), you can experience this side effect even at low doses (doses that aren’t sufficient to help you feel better). It can sometimes be managed by switching to sustained-release T3.
- Rapid heart rate: The more T3 that you take, the faster your heart will beat, for the same reasons mentioned above. Unfortunately, your heart rate may increase when taking T3 before the other tissues in your body get what they need.
- Anxiety and overstimulation: Compared to T3 supplements, T3 medications may cause anxiety and even increase your risk of panic attacks. This typically occurs when your dose is too high.
- Hair loss: T3 medications like Cytomel are known to cause temporary hair loss that lasts for around 3-6 months (6). This side effect is often very disturbing to women, especially those who already have low-thyroid-related hair loss. The good news is that it is usually temporary, the bad news is that your hair gets worse before it gets better.
- Insomnia: Due to their stimulation, T3 medications may lead to the inability to fall asleep and stay asleep.
- Stomach upset: Because T3 thyroid hormone increases acid production (7), it can lead to an upset stomach that is different from T3 support supplements. This side effect tends to linger and is dose-dependent.
- Increased sweating: The more T3 you take, the more heat your body will produce, which may lead to sweating. This can usually be solved by reducing your dose, but women in menopause become more susceptible to hot flashes when using T3.
- Weight loss: This is one of the main benefits of using T3, but it’s worth noting that an excessively high dose of T3 can lead to muscle wasting and a catabolic state which is counterproductive for those with thyroid problems.
Some more serious, but less common side effects, include:
- Bone loss: Long-term use of excessively high doses may increase your risk of bone loss (8) through increased bone turnover.
- Atrial fibrillation: If you take too much T3, you may put yourself at risk for developing atrial fibrillation (9). This side effect may be due to the impact that T3 has on heart size/volume.
- Heart enlargement: This is very rare and only occurs at high doses, but I’ve seen a few cases. The good news is that your heart returns to normal size once you stop taking T3.
These may seem more serious and dangerous, but let me put them into perspective:
You have around a 30% chance of experiencing a mild unwanted side effect when using T3 medication versus about 5% when using a T3 boosting supplement.
So there is increased risk and increased severity, but not enough to negate their benefits.
Should You Take Both T3 Supplements AND Medications?
This is where things get interesting. And for most thyroid patients the answer is yes.
Here’s why:
- They have complementary actions: Supplements help your body create more T3 on its own while medications provide you with direct T3. But there’s no reason you can’t benefit from both of these things at the same time.
- Potentially lower medication doses: By supporting your body’s ability to create its own T3, you become less reliant on your medication, meaning you can get by with a lower dose. The lower your dose, the less likely you are to experience side effects.
- More stable T3 levels: T3 medications cause a spike in serum T3 a few hours after you take them. Supplements, on the other hand, provide a more sustained and mild increase over time. Taking both simultaneously means more stable T3 levels day to day.
- T3 supplements support T3 medications: Some thyroid patients have issues with both T3 production and T3 cellular sensitivity. Taking supplements with the right ingredients can help your cells more effectively use the T3 found in your medication, thereby improving your results.
Your Next Steps
Optimizing your T3 status can not only help you feel better but also help you deal with some of the most frustrating low thyroid-related symptoms like weight gain.
It’s my experience that most thyroid patients do better when using both options together, but getting T3 medication is no easy task.
Which is why I put together a list of research-backed ways that you can naturally increase your T3 status.
If you want to do that, read this article next.
Scientific References
#1. https://pmc.ncbi.nlm.nih.gov/articles/PMC4044302/
#2. https://www.ncbi.nlm.nih.gov/books/NBK285568/
#3. https://www.ncbi.nlm.nih.gov/books/NBK500006/
#4. https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/010379s054lbl.pdf
#5. https://pmc.ncbi.nlm.nih.gov/articles/PMC8570994/
#6. https://pmc.ncbi.nlm.nih.gov/articles/PMC10492440/
#7. https://pubmed.ncbi.nlm.nih.gov/12754530/
#8. https://pmc.ncbi.nlm.nih.gov/articles/PMC7640752/
#9. https://pmc.ncbi.nlm.nih.gov/articles/PMC9242705/
