T4 (Levothyroxine) Complete Guide: Dosage, Differences, Benefits, and Side Effects

 »  »  T4 (Levothyroxine) Complete Guide: Dosage, Differences, Benefits, and Side Effects

  1. What is T4?
  2. How Does T4 Work?
  3. Bodybuilding and T4
  4. T4 vs T3
  5. Benefits
  6. Side Effects
  7. T4 for Women
  8. Dosage
  9. FAQ (Frequently Asked Questions)
  10. Conclusion

Have you ever wondered how some bodybuilders and fitness models are able to lose weight so quickly in the weeks or months leading up to a competition or photoshoot?

While the key variables that contribute to this process include rigorous eating and intense training, many professional athletes will choose to employ chemicals that speed the weight loss process in order to make weight for a competition or shed enough body fat for their on-stage appearance.

T4 is one of the most effective fat-burning supplements available. In this post, we’ll go over the active thyroid hormones T3 and T4 in more detail, as well as why bodybuilders need them throughout contest preparation.

What is T4?

Because your metabolism is considerably enhanced while taking T4 sodium, it is an effective fat burner. Because your metabolism is going haywire, you can afford to be a little sloppy on precontest dieting because it will still burn fat even if you eat a lot of calories. T4 is a thyroid hormone that has been synthesized (Type T-4). This substance is normally sold in bottles of 100 pills, each containing 100 mcgs. It comes in a variety of dosages, ranging from 5 to 100 mcgs. for each pill

This substance is popular among bodybuilders for a variety of reasons. Because your metabolism is considerably enhanced while using this substance, it is an effective fat burner. Because your metabolism is going haywire, you can afford to be a little sloppy on pre contest dieting because it will still burn fat even if you eat a lot of calories. Step over Ripped Fuel, Thermodrine, and the E/C/A stack.

This is the single finest fat-burning combo available today when used with clenbuterol (with the possible exception of DNP). Because it is such a good assist for protein synthesis, it also helps to make steroids more effective. Most people should start with a low dose of approximately 50 micrograms. Each day for the first 5-6 days, then increase by one tab or 50 mcgs per day every 5-6 days. 

Make sure you stay within the range of 100-200 mcgs. maximum of once per day Divide the tabs evenly across the day if you’re taking multiple tabs (e.g., 200 mcgs. would be 4 doses of 50 mcgs. each spaced evenly across the day).

 You must also ensure that you gradually wean yourself off of this product in order to maintain optimal thyroid function. Also, don’t take it for more than 5 weeks at a period. After completing a cycle of this medicine, wait at least 8 weeks before starting another to allow your thyroid to return to normal.

How Does T4 Work?

T4 is a synthetic version of thyroxine, a hormone produced naturally by the thyroid gland in the body. In those whose thyroid glands do not produce enough thyroxine naturally, T4 substitutes the missing thyroxine.

Thyroid hormones (such thyroxine) are important for our regular growth and development, as well as the maturation of our brain, spinal cord, nerves, and bone. Thyroid hormones are involved in both cell function and cell disintegration.

They also play a role in mood regulation, reproductive function, metabolism, and gastrointestinal function. When used to treat hypothyroidism (low thyroid levels), T4 is usually taken for the rest of one’s life unless the cause is temporary.

Bodybuilding and T4

Over the course of a year, researchers in Finland evaluated the response of the pituitary-thyroid system before, during, and after strength training on elite weightlifters. The findings, which were published in the “Journal of Sports Science” in 1993, revealed that times of reduced training result in a slight reduction in serum T4 concentrations 4. 

T4 levels in weightlifters were lower at night than in a control group, according to a 1995 study published in the “European Journal of Applied Physiology and Occupational Physiology,” which the researchers thought could have ramifications for muscle growth 5. Male bodybuilders who used androgenic-anabolic steroids were also shown to have minor thyroid impairment.

Thyroid medication is commonly used by bodybuilders preparing for competitions to help them shed fat by increasing their basal metabolic rate and getting “cut,” or producing maximum muscle definition. T4 may contribute to increased muscle retention and boost the effects of growth hormone in weightlifters who are also taking growth hormone, despite the fact that T3 is more popular for this purpose. 

Extra thyroid hormones in the body can aid in weight loss in the short term, but once thyroid supplements are discontinued, the excess weight loss is usually restored, according to the American Thyroid Association 2.

T4 vs T3

The thyroid gland, which is located in the neck, has an impact on a number of activities, including brain development, heart function, and digestion. T3 and T4 are active hormones that play an important role in metabolic regulation. T4 is produced in greater quantities than T3 and serves as a precursor to T3.

Around 40% of T4 in the body is changed to T3 through the process of removing an iodine group from its outer ring. Once converted, T3 is used by the body’s cells to supply oxygen and generate energy within tissues and glands. The thyroid produces 20% of the total T3 produced by the body. The remaining 80% is produced in various tissues outside of the gland.

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Hypothyroidism is the most common ailment treated with it T4 (low thyroxine levels in the body) but here are a few other benefits that T4 can provide:

  • Maintains appropriate cognitive and physical growth and development by replacing or supplementing low or absent thyroxine.
  • Returns thyroid levels to normal in children born with hypothyroidism, averting negative consequences on cognitive and physical development. The ideal hormone for hypothyroidism is T4, according to American recommendations.
  • Except for temporary hypothyroidism induced by subacute thyroiditis, it is beneficial for all types of hypothyroidism (an inflammatory disease of the thyroid most likely caused by a virus). Goiter and some thyroid malignancies may also be treated with this drug.

Side Effects

T3, T4, or T3:T4 combination compounds should not be used on their own to increase fat loss in people who already have a thyroid issue. Instead, they should speak with a medical practitioner beforehand, as certain substances may aggravate their illness. 

Unfortunately, many athletes rely on T3 as a crutch to lose body fat while neglecting to prioritize their nutrition and training. This may raise the chance of a major loss of lean mass, as well as negatively impact a competitor’s appearance by making them appear flat on stage.

The following are some other typical negative effects of utilizing T3 or a T3:T4 combination for weight loss:

  • Rapid heart rate (particularly in people who take more than 50mcg per day)
  • Increased muscle breakdown (why squander all of your hard work?)
  • Insulin sensitivity is reduced (this is not good news, especially for those who are trying to feed into their show and fill-back up)
  • Sweating excessively (talk about night sweats!)
  • Impaired cognition and increased agitation (the absolute worst thing to go through when you’re already hungry) are two of the most common side effects
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T4 for Women

It is safe to use T4 throughout pregnancy. It is critical that you continue to take T4 throughout your pregnancy. Thyroid hormone levels that are either low or too high during pregnancy might cause difficulties for both you and your baby. During pregnancy, you’ll need to undergo regular blood tests to ensure you’re on the proper dose of T4. While you’re pregnant, your doctor may need to raise your T4 dose.

It is safe to breastfeed while taking T4. Breast milk contains thyroid hormones as a natural component. When taken as a supplement, they only enter into breast milk in trace amounts, which are insignificant enough to have no effect on your infant. If you’re breastfeeding, it’s critical to keep taking T4 because it’s replacing what your body would normally produce. 

Thyroid hormones are required for your body to produce adequate breast milk for your baby. If you find that your baby isn’t feeding as well as normal, or if you have any other worries about your infant, contact your midwife, health visitor, pharmacist, or doctor right away.

Most adults and children can take T4. Some folks, however, will not be able to use it. If you’ve had any of the following symptoms, talk to your doctor before taking T4:

  • Any medicine, including T4, can cause an allergic response.
  • Too much thyroid hormone is produced by an overactive thyroid (thyrotoxicosis)
  • Adrenal gland-related health problem (your doctor will be able to tell you if you’re not sure)
  • Angina, heart illness, or heart failure are all examples of cardiac problems.
  • Blood pressure that is too high
  • Heart attacks in the past
  • Diabetes since T4 can boost blood sugar levels, your diabetes treatment dose may need to be adjusted.


Dosages of T4 Should Be Given As Follows:

Adult and Pediatric Dosage Forms & Strengths

Tablet form of medication

  • 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg
  • 25 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg

Capsule (Tirosint) form of medication

  • 13 mcg, 25 mcg, 50 mcg, 75 mcg, 88 mcg
  • 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg

Powder for injection form of medication

  • 100 mcg/vial
  • 200 mcg/vial
  • 500 mcg/vial


Should I follow any special dietary guidelines?

Some meals and beverages, especially those containing soybeans, walnuts, and dietary fiber, may have an effect on how T4 works for you. Before eating or drinking these foods, consult your doctor. 

What should I do if I forget to take my medication?

As soon as you recall, take the missed dose. If the next dose is approaching, skip the missing dose and return to your regular dosing plan. To make up for a missing dose, do not take a double dose.

What additional details should I be aware of?

Keep all of your doctor’s and laboratory appointments. To monitor your reaction to T4, your doctor will conduct a series of lab tests. Find out what your medication’s brand and generic names are. 

Is it okay if I drink beer with it?

While taking T4, you can consume alcohol. This medicine’s effectiveness is unaffected by alcohol. Alcohol, on the other hand, may exacerbate T4 adverse effects such as headaches, flushing, or sweating.

Is it legal for me to drive or ride a bike with it?

Yes, taking T4 will not impair your ability to drive or ride a bicycle.

How long does it take for T4 to start working?

T4 begins to act right away, but it may take a few weeks for your symptoms to improve and for you to notice a difference.


T4 is the preferred drug for treating hypothyroidism since it restores the missing thyroxine. T4 dosage must be customized to each individual, and there is a narrow line between taking too much thyroxine, which can cause harmful side effects, and taking too little, which can cause reduced functionality.

A blood test will be performed by your doctor before you begin taking T4. You’ll undergo regular blood tests once you start taking the treatment to see how well it’s working. During pregnancy, T4 doses must be closely controlled. It’s critical to speak with your doctor if you’re planning to become pregnant or suspect you might be pregnant in order to get the best treatment for you 

and your baby.

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The information provided above is not intended to substitute professional medical advice, diagnosis, or treatment. Always seek your physician’s advice or another qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have seen or read. We bear no responsibility or liability for your use of any compound.