T3 and T4 for Weight Loss + Bodybuilding

T3 for Bodybuilding

Curious about how some bodybuilders and fitness models achieve rapid weight loss before contests or photoshoots? 

While strict dieting and intense training play major roles, many elite athletes turn to compounds that accelerate weight loss. 

One such tool is T3, also known as Cytomel while another is T4, also known as Synthroid. In this article, we delve into the active thyroid hormones T3 and T4 and why bodybuilders use them during contest prep. 

We’ll explore potential side effects and how athletes can restore natural thyroid hormone production post-prep. 

Now, let’s dive into the world of T3 and T4 for weight loss and bodybuilding!

The information provided in this article is for general informational purposes only. We do not recommend or endorse the use of steroids or illegal compounds for performance enhancement and weight loss.

Key Takeaways

  • T3 and T4 are biologically active thyroid hormones crucial for regulating metabolism. πŸ‹οΈβ€β™‚οΈ
  • Bodybuilders and fitness models utilize synthetic T3, T4, or T3:T4 combos to rapidly shed body fat pre-contest or photoshoot. πŸ’Š
  • Potential side effects of T3 and T4 include elevated heart rate, excessive sweating, sleep disturbances, and lean mass reduction. πŸ˜“
  • T3 can be taken alone or combined with T4 to enhance fat loss effectively. πŸ”„
  • It’s essential for athletes to prioritize health and consult professionals before incorporating T3 and T4 for bodybuilding purposes. 🩺

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T3 and T4 for Weight Loss + Bodybuilding

The thyroid gland is located towards the base of the neck and influences a wide variety of bodily processes including brain development, heart function, and digestive function.

It produces the biologically active hormones T3 and T4 which play a major role in regulating metabolism.

T4 (thyroxine) is produced in higher amounts than T3 (triiodothyronine) and functions as a T3 precursor.

Around 40% of T4 in the body is converted into T3 through the process of removing an iodine group from its outer ring (deiodination).

Once converted, the body’s cells use T3 to deliver oxygen and generate energy within various tissues and glands within the body.

The thyroid gland generates 20% of the body’s total T3 whereas the remaining 80% is created outside of the thyroid gland in other tissues.

Most people secrete between 10-22 mcg T3 and 94-110 mcg T4 each day.

Hypothyroidism vs Hyperthyroidism

Some individuals may be affected by thyroid conditions including hypothyroidism or hyperthyroidism.

In most cases, these conditions are caused by autoimmune diseases but they may also be heavily influenced by dietary deficiencies, surgeries, or the use of certain medications.

Hypothyroidism is a condition where the thyroid is underactive and does not produce adequate amounts of thyroid hormones.

Most individuals tested for hypothyroidism will display low levels of free T3 and free T4 while their TSH (thyroid stimulating hormone) levels are high or test outside of the optimal reference range.

In contrast, hyperthyroidism is a condition where the thyroid is overactive and produces excessive amounts of T4 (thyroxine).

Individuals who test for hyperthyroidism typically have extremely low levels of TSH while their free T3 and free T4 levels are elevated.

Cytomel and Synthroid

T3 and T4 for Weight Loss

Those who are affected by one of the above thyroid conditions will generally need to take medication to obtain proper thyroid function.

Individuals with hypothyroidism will usually take Synthroid (synthetic T4), Cytomel (synthetic T3), or combination thyroid medication that contains both synthetic T3 and T4.

Synthroid, or Levothyroxine, is prescribed by most doctors for the treatment of hypothyroidism as it provides a milder approach and tends to result in fewer side effects.

However, Cytomel, or Liothyronine, may also be prescribed for hypothyroidism and provides a more aggressive form of treatment.

Some doctors and medical experts tend to shy away from the use of Cytomel as T3 is absorbed rapidly and may lead to mild thyroid hormone toxicity in certain patients.

On the other hand, the use of combination thyroid medication has been on the rise within the last few years and is viewed by many medical experts as a promising solution for thyroid hormone management.

Doctors within North America have noticed an increase in patient dissatisfaction with the use of monotherapy (i.e. synthetic levothyroxine only) and nearly 1/3 of physicians within the US provide treatment in the form of combined T3:T4 therapy.

In fact, a recent study showed that 23 patients who switched to the use of combination therapy over monotherapy displayed major improvements in quality of life and cognitive function.

Cytomel Weight Loss

Due to the more aggressive nature of Cytomel compared to Synthroid, many bodybuilders have used it as a tool for rapid weight loss in order to enhance their performance, make weight, or shed necessary body fat to obtain their desired physique.

Individuals who are not affected by hypothyroidism may obtain synthetic T3 on either the black market or by purchasing it from websites that sell research compounds, such as peptides, SARMs, and the like.

These athletes may choose to purchase T3 in Cytomel form or they may find it in a generic liquid, capsule, or tablet form.

T3 Dosage Bodybuilding

T3 for Bodybuilding
Dosage GuidelinesDuration
πŸ‹οΈβ€β™‚οΈ Start with 12.5mcg
βž• Increase by 12.5mcg every 3 days
⏰ Maximum dosage: 50mcg8 weeks
πŸ”„ Taper off graduallyAfter contest

Athletes typically run anywhere from 25-50 mcg on average over the course of 8 weeks to enhance fat loss.

If using a tablet or liquid form, competitors will generally start their dosage at 12.5mcg and then gradually increase their daily dosage by 12.5mcg every 3 days until they reach 50mcg.

They will continue to run 50mcg through the end of their contest, however, some coaches may slowly lower their clients’ dosage a few weeks prior to competition in order to reduce the loss of lean mass or prevent muscles from flattening out the day of the show.

After the completion of their contest, most competitors will use the same protocol for tapering off and drop their daily dosage by 12.5 mcg every 3 days and run the final 3 days of their T3 cycle at 12.5mcg total.

Those who opt for capsule form may choose to run 25mcg for the entire duration or they may follow a similar tapering method depending on each capsule’s concentration.

In most cases, capsules are extremely hard to dose properly, especially if they contain higher amounts of T3, such as 50mcg per capsule.

You won’t see most bodybuilders or fitness models purchasing Synthroid or generic T4 to enhance their physique as T3 is nearly 5x more potent than T4 and under normal conditions, the body only converts up to 40% of T4 into T3.

T4 Bodybuilding Dosage

Dosage GuidelinesRatio
πŸ‹οΈβ€β™‚οΈ Optimal ratio: 1:2 (T3:T4)
πŸ’§ Liquid form: 30mL bottle
πŸ’‰ Each mL contains: 100mcg T3 and 200mcg T4
⚠️ Do not exceed:0.5mL per day

If using a T3:T4 combo, it’s best to purchase a product that contains a 1:2 ratio.

For example, some competitors will use this thyroid hormone combo in liquid form.

Each bottle typically contains around 30mL and each mL should contain around 100mcg:200mcg of T3 and T4 respectively.

However, it’s best to not exceed a limit of 50mcg:100mcg so competitors should usually only need to use about 0.5mL per day once they’ve reached the peak of their cycle.

Cutting Stacks: T3 and T4 for Weight Loss + Bodybuilding

In order to enhance fat loss further, some competitors may choose to add on additional compounds during their T3 or T3:T4 cycle.

Here’s a quick glimpse into 2 popular stacks used by bodybuilders during the final weeks of contest prep for a final push.

Clen T3 Cycle

Clenbuterol (clen) combined with T3 is extremely powerful and can further fuel the fire in respect to thermogenesis.

Since T3 is typically limited to 8 weeks of use, competitors may start using clen around 12-16 weeks out from their show.

The starting dosage is usually around 20mcg daily and should be increased in 20mcg increments every 2 weeks until reaching 120mcg.

It’s best to take clen before fasted cardio in the mornings as it will promote better breathing and expand blood vessels.

Some coaches may recommend that their athletes only use clen for 2 days on 1 day off to maintain maximum effectiveness and prevent adrenal fatigue which would hinder the fat loss process.

Clen Yohimbine T3 Stack

Perhaps an even more effective cutting stack for those who can handle it is the use of clen, T3, and yohimbine.

Generally, competitors will only need to use 5mg of yohimbine pre-workout or before fasted cardio and they may use yohimbine on their days off of clen.

An example of how a bodybuilder may use clen and yohimbine together while on T3 is to alternate 2 days on clen followed by 2 days on yohimbine HCL.

Clen should be used in the same way that it would on a T3-clen cycle whereas yohimbine should be taken once or twice daily before training and fasted cardio in 5mg dosages.

Some people may be sensitive to yohimbine so it’s best to test your tolerance to this supplement prior to trying it during contest prep.

T3 and T4 for Weight Loss + Bodybuilding Side Effects

T3 for Bodybuilding

Individuals who currently have a thyroid disorder should not utilize T3, T4, or T3:T4 combination compounds on their own to accelerate fat loss.

Rather, they should consult with a medical professional first as the use of particular compounds may worsen their condition.

Unfortunately, many athletes use T3 as a crutch for attempting to drop body fat while not prioritizing their diet and training.

This may increase the risk for a significant reduction in lean mass and may actually affect a competitor’s look negatively by causing them to look flat on stage.

Some other common side effects of using T3 or T3:T4 combo for weight loss include:

  • Rapid heart rate (especially in those using over 50mcg/day)
  • Increased breakdown of muscle (why waste all of your hard work away?!)
  • Reduced insulin sensitivity (this is not good news, especially for those who are trying to feed into their show and fill-back up)
  • Excessive sweating (Talk about night sweats!)
  • Impaired cognition and increased agitation (the absolute worst thing to experience when you’re already hangry)

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Thyroid Storm Management

If you’re one of many competitors who are lucky enough to experience a thyroid storm when taking T3 then you know firsthand how difficult it can be to manage side effects effectively and find sweet relief.

Many newbies to T3 may experience nausea, excessive sweating, elevated temperature, and agitation within the first few days of its use.

If this occurs, lower your starting dosage by 25-50% and then follow the gradual 3-day taper of increasing your dosage by 12.5mcg, if possible.

You may choose to raise your dosage at somewhat smaller dosages if necessary but generally, 12.5mcg works for most people.

This happens quite frequently as your body is still producing endogenous thyroid hormones while taking exogenous synthetic thyroid hormones, thus creating an excess supply of thyroid hormone available for the body to use.

It usually takes at least several days up to a few weeks for the body to shut down its own production of thyroid hormones after starting T3 so it’s acceptable for most people to start at lower dosages for the first 2 weeks of their T3 cycle.

If a thyroid storm doesn’t occur until the peak of your T3 cycle you may be running too high of a dosage (this typically occurs if you exceed 50-75mcg per day).

If you need to lower your dosage at any point throughout your cycle make sure to slowly reduce the dosage and maintain a minimum of 25mcg per day so that your body maintains a similar T3 production as it did prior to taking synthetic thyroid hormones.

Thyroid Recovery

T3 and T4 for Weight Loss

At the conclusion of your T3 cycle, it’s absolutely essential for you to restore your body’s natural production of thyroid hormones.

In order to do this, it is recommended to take specific vitamins and minerals as well as ensure that you’re sleeping enough each night and recovering properly to lower cortisol.

Some of the top nutrients to consume in foods or supplements following the use of synthetic T3 and T4 include the following:

  • Iodine
  • Selenium
  • L-tyrosine
  • Zinc
  • Magnesium
  • Iron
  • Vitamin D
  • B Vitamin Complex
  • Antioxidants (vitamins A, C, E, etc.)

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Complete Thyroid Panel

We recommend Lets Get Checked for getting a full at-home thyroid panel, it’s super convenient since you don’t have to go to the center and wait in line etc. However, they don’t test for rT3 (reverse T3).

You should also make sure to obtain a complete thyroid panel every few months post-contest to check to see if you’ve restored proper thyroid function.

Make sure that you ask for the following parameters when getting a thyroid panel as they will detect any abnormalities and provide a full spectrum of evidence for potential disorders:

  • Free T3 (fT3)
  • Reverse T3 (rT3)
  • Free T4 (fT4)
  • Thyroid Stimulating Hormone (TSH)

Bonus Section – 5 Secret Protocols Bodybuilders Use to Get Ripped!

This portion of the article was written by Ernst Peibst. Check out more of his work here!

Bodybuilders and fitness models today are more shredded than ever before!

Back in Arnold’s day you could compete in a Mr Universe at 10% body fat and no one would bat an eye.

Nowadays, if you compete carrying anything more than 5% body fat, you’ll look tragically out of place!

So how do they do it?

How do they get so ripped and attain such low levels of body fat…

Water Manipulation

When you see a fitness model or bodybuilder onstage, they don’t look like that all year round. It’s almost impossible (and unhealthy) to stay at extremely low body fat percentages all year round (<5% BF). However, there’s another protocol they use to look even more shredded than usual…

They will manipulate their water intake to appear more ripped in time for a contest.

By reducing the amount of water that collects outside their muscles, they will appear more toned, with enhanced vascularity and more frequent striations. Instead of looking smooth/bloated/puffy, they will appear dry and grainy.

They do this by increasing their water intake dramatically a week or so out from the competition. They typically will gulp down up to 2 gallons of water a day. This will literally turn their bodies into human water fountains.

As the body becomes concerned with the amount of water being consumed; as a self-defense mechanism, the body will urinate very frequently in a bid to reduce water weight.

Then roughly 24 hours or less before a competition, the competitor will cut all water intake. Consequently, the body will continue flushing out water, resulting in the bodybuilder looking very dry and shredded.

After 24 hours, the body detects that the person is no longer drinking large volumes of water, and as a result the body will start to retain fluid again.

Such water manipulation protocols will create an illusion of the person looking much leaner, compared to how they looked a week ago. In reality, their body fat percentage has stayed roughly the same; yet they’ll appear more shredded.


Diuretics are often used by bodybuilders when prepping for a show, to expel even more water and enhance muscle definition.

Unfortunately, diuretics have led to many hospitalizations and deaths of athletes, due to dehydration and electrolyte imbalances. Andreas MΓΌnzer is one of a number of bodybuilders who died from drugs, with diuretic-use thought to have played a role.

andreas munzer ripped
Andreas MΓΌnzer

Andreas was known to be one of the most shredded bodybuilders in the history of the sport, taking the art of being ripped to a whole new (uncomfortable) level.

Following his death, his electrolytes were found to be out of wack and his potassium levels were abnormally high.

T3 and Cytomel Supplements

T3 (Triiodothyronine) is a hormone produced by the thyroid gland. T3 has a very powerful effect on a person’s metabolism and their ability to burn fat. Simply put, the more free T3 you have, the more fat you’ll burn.

Hypothyroidism is very popular right now with people not able to produce sufficient amounts of this hormone, preventing weight loss. This is particularly prevalent in females.

Many bodybuilders take thyroid medications, such as Cytomel, to take advantage of this fat-burning opportunity; revving up their level of T3 and getting super shredded.

Your body naturally produces about 25mcg of T3 each day, however if your level is considerably less than this, your doctor may prescribe you exogenous T3 (Cytomel).

Mr Olympia legend Lee Priest has admitted to taking T3 drugs in the past (1), using 25-50mcg of Cytomel a day leading up to a competition.

lee priest

The downside to using T3 is it can suppress your natural production of this hormone (like steroids). Thus, users may find it difficult to burn fat AFTER using T3. However, endogenous T3 production should recover after several weeks or months of use.

Low T3 levels are possible long-term, if a bodybuilder abuses T3 or doesn’t take enough time off this medication.

In this case, a deficiency in this hormone may blunt fat loss, even if the person eats in a calorie deficit.

Fat Burners

Banned fat burners such as ephedra or clenbuterol, are also used by fitness models and bodybuilders to shed fat.

These are stimulants which rev up the central nervous system, which in turn spikes a user’s metabolism. Neither of these fat burners is FDA-approved, due to their causing severe cardiovascular and psychological effects.

Such side effects include:

  • Increased heart rate
  • Increased blood pressure
  • Nervousness
  • Anxiety
  • Depression

Fat burners won’t transform a guy at 20% body fat into Frank Zane. But they can help bodybuilders bust through fat loss plateaus when dieting, helping them get extra shredded. Thus, they are often incorporated at the end of a cut, rather than at the beginning.

Natural fat burners, which often contain caffeine replicate the same physiological process as ephedra and clenbuterol, however their effect is a lot more mild.

Equally, side effects from natural fat burners are considerably less and thus are safer to take.

Steroids & PEDs

Over 50% of male bodybuilders take steroids to help them get ripped (2). This number would almost certainly be 100%, if just testing elite bodybuilders, competing in competitions such as Mr Olympia and the Arnold Classic.

Steroids bodybuilders use to reduce body fat include: winstrol, anavar, testosterone, trenbolone, halotestin, masteron, primobolan and turinabol.

Today, even women will buy anavar, among other female-friendly steroids, in a bid to tone up and build lean muscle. It isn’t just female bodybuilders using these steroids either, but also Instagram models and women who simply want to look good.

Some of these steroids have diuretic attributes, helping to rid the body of water, as well as fat. They also have anabolic properties, enabling users to retain their muscle tissue and strength levels as they diet down.

Compounds such as anavar also increase glycogen storage inside the muscles, helping to keep the muscles looking full and vascular, even when on low calories. This effect is so extreme, that the pumps on anavar can be unpleasant.

This ‘full look’ is seldom seen in natural bodybuilders, often looking depleted and lacking vascularity when cutting aggressively.


In the world of bodybuilding, where every ounce of fat matters, T3 and T4 play significant roles. These thyroid hormones, especially T3, are sought after for their fat-burning properties.

However, their usage comes with potential risks, including heart rate elevation and muscle loss. Understanding the science behind T3 and T4 is crucial for athletes aiming to optimize their performance and physique.

Remember, always prioritize health and consult with professionals before incorporating any supplements, especially T3 and T4 for bodybuilding purposes.

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American Association for Clinical Chemistry (AACC). (2017, March 20). Thyroid Hormone Synthesis and Transport. https://www.aacc.org/science-and-research/clinical-chemistry-trainee-council/trainee-council-in-english/pearls-of-laboratory-medicine/2017/thyroid-hormone-synthesis-and-transport

Dayan, C., & Panicker, V. (2018). Management of hypothyroidism with combination thyroxine (T4) and triiodothyronine (T3) hormone replacement in clinical practice: a review of suggested guidance. Thyroid research, 11(1), 1-11. https://thyroidresearchjournal.biomedcentral.com/articles/10.1186/s13044-018-0045-x

Iddah, M. A., & Macharia, B. N. (2013). Autoimmune thyroid disorders. International Scholarly Research Notices, 2013. https://www.hindawi.com/journals/isrn/2013/509764/

InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. How does the thyroid gland work? 2010 Nov 17 [Updated 2018 Apr 19]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279388/

Mayo Clinic. (2020a, November 14). Hyperthyroidism – Symptoms and causes. https://www.mayoclinic.org/diseases-conditions/hyperthyroidism/symptoms-causes/syc-20373659

Mayo Clinic. (2020, November 19). Hypothyroidism – Symptoms and causes. https://www.mayoclinic.org/diseases-conditions/hypothyroidism/symptoms-causes/syc-20350284

Paloma. (2021, May 21). Top 6 Vitamins for Hypothyroidism. Paloma Health. https://www.palomahealth.com/learn/top-vitamins-hypothyroidism

Paloma Health. (2021). Thyroid drugs for hypothyroidism | Paloma Health. https://www.palomahealth.com/medication

Rousset, B., Dupuy, C., Miot, F., & Dumont, J. (2015). Thyroid hormone synthesis and secretion. Endotext [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK285550/

Senese, R., Cioffi, F., de Lange, P., Goglia, F., & Lanni, A. (2014). Thyroid: biological actions of nonclassical thyroid hormones. The Journal of endocrinology, 221(2), R1-12. https://joe.bioscientifica.com/view/journals/joe/221/2/R1.xml

(1) https://www.youtube.com/watch?v=FDYXf_ukRFs

(2). https://www.ncbi.nlm.nih.gov/pubmed/2621538


Daniel Louwrens BSc PT

Daniel Louwrens BSc PT | Writer

Daniel Louwrens is a well-rounded fitness professional with over 10 years of experience in bodybuilding and fitness. He holds a BSc in Chemistry from the University of Western Cape and is a certified International Personal Trainer and Nutritionist. He is also a skilled bodybuilder and head coach for Muscle and Brawn. With his knowledge and expertise, he provides personalized training, nutrition, and recovery guidance to help clients reach their fitness goals.

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