Approved for one thing, at a dose that is no longer sold
What it actually is
Your brain makes a small signalling molecule called growth hormone releasing hormone. It lands on a small gland at the base of your skull and makes that gland put out a burst of growth hormone. Tesamorelin is a lab made copy of that signal, altered so that it lasts longer in the blood after an injection. It is an approved medicine: the United States regulator cleared it in November 2010 under the brand name Egrifta, for the excess deep abdominal fat that builds up in some adults with HIV, the virus that causes AIDS. That is the entire approval, one problem in one group of people, and the label itself says it is not for weight loss because its effect on weight is neutral.
What it is supposed to do
It copies the body's own instruction to release growth hormone, so the gland puts out more of your own rather than the injection supplying any. When that growth hormone reaches the liver, the liver answers with a growth signal of its own called insulin like growth factor 1, and that rise is the clearest measured effect: in the first large trial it went up 81.0 percent on the drug and fell 5.0 percent on the dummy injections. What actually moves is one particular fat store, the deep fat behind the abdominal muscle wall and around the organs, which fell 15.2 percent over 26 weeks while rising 5.0 percent on the dummy. Off the drug it comes back: in the extension phase of the second trial, the group switched from drug to dummy put 24 square centimetres of that deep fat back on, while the group kept on it lost a further 11.
What people take it for
Inside the approval it is prescribed to adults with HIV for excess deep abdominal fat. Outside it, people buy it to lose belly fat, some for liver fat, and some for thinking and memory, that last one resting on a single study in which 152 adults aged 55 to 87, 66 of them with mild cognitive impairment, were given 1 mg under the skin half an hour before bed for 20 weeks. That same study is where the advice to inject before bed comes from. Outside the indication it also gets run in cycles, some weeks on and some weeks off, which is a pattern no trial has used, because every trial dosed it every day without a break.
The dose question
What circulates
2 mg a day, from grey market vials, run in cycles
What was studied
2 mg a day, continuously, for 26 weeks to a year
Falutz 2007 in 412 adults with HIV, plus three later trials at the same dose
The number matches the dose in every published trial, and the product it was approved for is gone. What is sold as medicine now is 1.4 mg a day, and 1.28 mg in the version that replaced it, in formulations both labels call not substitutable. Every trial dosed continuously, and no published evaluation of the weeks on, weeks off cycling turned up.
Reported because it is what people use. Nothing here recommends any amount.
How long it lasts
This entry gives no figure for how long it lasts in the body. What it says is that the molecule is a copy of the body's own signal, altered to last longer in the blood after an injection, and that every trial gave it once a day.
Route studied
Injected under the skin, once a day without a break, in trials running 26 weeks to a year
Route used
Injected under the skin at home, from grey market bottles, often in cycles of some weeks on and some weeks off
How to check you have the right molecule
This entry publishes no molecular weight and no sequence to hold a laboratory report against, so the checks it gives are on paperwork and on wording. The first is the number on the label. The 2 mg a day everyone quotes was approved in 2010 for a product that is no longer sold. What is sold as medicine now is Egrifta SV at 1.4 mg once a day, and Egrifta WR, approved in March 2025 to replace it, at 1.28 mg, and both labels say the formulations are not substitutable: different powder strengths, a different number of small bottles per dose, different mixing steps, different storage. The second is the citation. If a seller points you at a record on the United States government's trial registry, go and read it, because the first result for tesamorelin and liver fat, NCT07481734, is a forgery that uses the word mock twice, once in its title and once in its description. The third is the name on the vial. Sermorelin, CJC-1295 and modified growth hormone releasing factor 1 to 29 are shorter copies of the same body signal, none of them has evidence like this one, and Egrifta's approval gets invoked for all of them.
Two mistakes, and they stack. The first is what the drug actually empties. There are two fat compartments in an abdomen and this one works on the store behind the muscle wall, around the organs, while in 806 pooled patients the layer directly under the skin, the stuff you can pinch, was essentially unchanged, a difference too small to separate from chance. Anyone buying it for how they look is paying to empty a compartment no mirror can show them. The second is the number. The 2 mg a day quoted as the approved dose belongs to a product that is gone, so measuring out of a grey market bottle to hit the approved 2 mg is aiming at something that no longer exists. Price is why people do it anyway: a Canadian review recorded a submitted price of $3,085 for a box of 60 bottles, a 30 day supply, against grey market listings around $150 for a 10 mg bottle.
What is known about harm
The safety figures that do not reach the sales copy are about that liver growth signal, insulin like growth factor 1. At 26 weeks, 47 percent of patients were more than 2 standard deviations above the average for their age and sex, and 36 percent were more than 3. A standard deviation score counts how far a result sits from the average, and above 2 is outside where nearly everyone healthy falls. The label tells doctors to keep measuring that hormone and to stop the drug if it stays above 3, which nobody buying research use only bottles can do. New high blood sugar, meaning a reading of 6.5 percent or higher on a test that reflects average blood sugar over about three months, showed up at week 26 in 5 percent of the treated group against 1 percent on the dummy. The trial abstracts report no change in blood sugar and the label reports this difference, and only the first one travels. What years of it do is unknown: the ten year study meant to settle tumour and cardiovascular safety, NCT01579695, enrolled 391 people, ran from February 2013 to August 2018, and stopped with the reason field left blank, and the longest anyone stayed on the drug inside the approval programme was 52 weeks.
The arithmetic
Tesamorelin is sold in 10 mg vials. Mixing errors put people an order of magnitude off using a perfectly good vial, and the arithmetic is simple enough to check yourself.
Vial
Water
Concentration
In 10 units
10 mg
1 mL
10 mg/mL
1 mg
10 mg
2 mL
5 mg/mL
500 mcg
10 mg
3 mL
3.33 mg/mL
333 mcg
10 units is 0.1 mL on a U-100 insulin syringe, whatever is in it. For any other combination, or to see the arithmetic worked out, use the calculator.
Everything on this page is a summary. The citations, the studies and the reasoning live in the full entry.