Liothyronine (T3)

What T3 does

T3 bodybuilding use rests on one fact: liothyronine is the active thyroid hormone, and supplying it directly bypasses the conversion step your body uses to regulate metabolic rate. It raises that rate substantially and reliably. This section holds 33 lines from £24 to £156, clustered near £57.

It works. The question is what it costs.

The trade-off

Elevated T3 is catabolic to muscle as well as fat. The tissue loss can be significant, and adequate protein plus resistance training limit it rather than preventing it. Someone running T3 in an aggressive deficit without both can lose a substantial share of total weight as lean tissue.

Your own thyroid also shuts down while you use it — the same feedback logic as anabolic steroids. Stopping abruptly after an extended run leaves you hypothyroid while the axis recovers: flat, cold and gaining weight easily, which is the opposite of the intended result. Short blocks with a taper recover more predictably than long continuous runs.

Against T4

Levothyroxine is the storage hormone your body converts as needed, so it preserves that regulatory buffer. T3 removes it. That is why T3 is faster and stronger, and precisely why it is riskier — the comparison is in T3 versus T4.

How it is typically used

Short blocks rather than continuous running, with a taper at both ends. The taper matters more here than with most compounds because stopping abruptly leaves you hypothyroid while your own axis restarts, and that period is uncomfortable and counterproductive.

It is also commonly paired with other fat-loss compounds, which is where the cardiac load stacks. Doing that without monitoring heart rate and blood pressure is the most common way this category causes real harm.

Where each compound fits

Oxymetholone and methandienone are mass compounds used in a surplus, both wet and both harsh. Stanozolol and turinabol are dry compounds used late in a cut, both harder on lipids than their reputations suggest. Oxandrolone sits alone as the one that is genuinely gentler on every axis except cost.

Matching the compound to the phase matters more than dose optimisation. Running a dry compound in a bulk, or a wet one before a show, produces disappointment that gets misattributed to product quality rather than to the choice.

The blood-pressure problem

Several compounds here drive blood pressure up through water retention, and it produces no symptoms until it is substantially elevated. A home monitor costs very little against what it detects, and it is the single most useful purchase alongside any oral cycle.

What to monitor

TSH, free T3 and free T4 before, during and after. Without those numbers you cannot tell whether you are mildly elevated or well into a range that damages muscle and heart, because the subjective experience is similar across a wide band. Combining with clenbuterol stacks cardiac load from two directions, which is common and poorly considered.

Euro Pharmacies and Dragon Pharma carry the stocked lines, listed as T3, Liothyronine, Cytomel and Thyro3. It is a prescription-only medicine in the UK.

Frequently asked questions

Is T3 better than T4 for fat loss?
Faster and stronger, because it bypasses the conversion step. That is also exactly why it is riskier.

Will my thyroid recover?
Usually, given time. Duration and dose are the main determinants; short blocks with a taper recover more predictably.

Does T3 burn muscle?
It is catabolic to lean tissue as well as fat. Protein and resistance training limit that rather than preventing it.

Can T3 be combined with clenbuterol?
People do, and it stacks cardiac load. Blood pressure and heart-rate monitoring stop being optional.

How long should a T3 run be?
Short blocks with a taper rather than continuous use, to limit both muscle loss and suppression.