What is T4 (Levothyroxine)?

T4 is a synthetic version of thyroxine, the main hormone your thyroid gland produces naturally. It was developed to treat underactive thyroid conditions, helping the body regulate metabolism, energy, and temperature. In performance circles, it's used to push the metabolism higher and support fat loss.

Quick Facts

How Does It Work?

T4 is a pro-hormone that your body converts into the active thyroid hormone T3. T3 then binds to receptors in cells throughout the body and directly speeds up your metabolic rate. This means your body burns through calories faster, even at rest.

What It's Used For

• Treating hypothyroidism (underactive thyroid)
• Accelerating fat loss during a cutting phase
• Helping the body process calories more efficiently alongside other compounds

What to Expect

You should notice an increase in body temperature, energy output, and a faster rate of fat loss over several weeks. Because T4 converts slowly to T3, effects build gradually rather than hitting all at once. Most users find it works best when combined with a calorie-controlled diet.

Possible Side Effects

• Increased heart rate or palpitations
• Excessive sweating and feeling overheated
• Muscle loss if dose is too high or diet is insufficient

Cycle & Dosage Notes

Most users start at 25 mcg per day and increase gradually over 2–4 weeks to find a comfortable dose. Cycles typically run 6–10 weeks, after which the dose should be tapered down slowly to allow the thyroid to recover. T4 is commonly used alongside anabolic compounds or fat burners to protect muscle while in a calorie deficit.

Storage

Keep at room temperature (15–25°C), away from light and moisture. Leave in the original packaging.

This info is for research and educational purposes only. Check the laws in your country before ordering.