Testosterone Undecanoate – Nebido brand by Bayer is not bodybuilding but rather medical product, unique by its properties due to extremely long action comparing to oral testosterone undecanoate (andriol/restandol) or androgel/testogel widely used for the testosterone replacement therapy purposes. It comes in 4 ml ampules, which contains 1000 mg of testosterone undecanoate in total. The active substance is testosterone undecanoate 250 mg/ml (corresponding to 157.9 mg of pure testosterone). The other ingredients are benzyl benzoate and refined castor oil. Nebido is a clear, yellowish oily liquid. The contents of the packs are: 1 amber glass ampoule with 4 ml solution for injection.
Testosterone is primary male sex hormone. Nebido is used for treating symptoms of testosterone deficiency, also known as hypogonadism in adult men whose testes do not produce enough of it.  Nebido works by replacing or supplementing endogenous testosterone production.
Low testosterone levels should be confirmed by two separate blood testosterone measurements and include following symptoms, which Nebido intends to cure: impotence, infertility, low sex drive, tiredness, depressive moods, bone loss caused by low hormone levels. In general, mild testosterone replacement therapy is advisable for men over 40, for men over 65 it`s vitally important since endogenous production becomes critically low.
Testosterone Undecanoate may also be used for other conditions as determined by your doctor.
Dosage and usage – medical and bodybuilding
According to the manufacturer, common Nebido dosage is single 1000 mg injection made every 10-14 weeks, i.e. ~4 times a year. Unfortunately, many physicians follow that claim and schedule. I do not pretend to be smarter than these doctors, however, there are no independent studies, proven this. Furthermore, bodybuilding is completely different story. Taking into consideration that half-life time of testosterone undecanoate is 21 day, in bodybuilding monthly, bi-weekly (or even weekly?) injections are advisable to maintain testosterone level stable. I`m not saying that it`s absolutely necessary to inject bi-weekly, but in general it`s much better than taking it once every 6 or even 12 weeks as stated by manufacturer. Disregarding of what ester you use – frequent injections is the best way to keep your test levels stable. Longer half life just means that you can do it less frequent comparing, for instance, to sustanon (3 shots / week) or enanthate (2 shots / week). Dosages in bodybuilding should be much higher than medical dosages, something like 1000 mg monthly, and this is one more point to use more frequent injections than stated by manufacturer. We do not advice higher dosages of nebido, if you need more effect, just use different testosterone forms.
But if this is a medical issue, take Testosterone Undecanoate only as directed. Discuss the point above with your GP, but final decision is up to him. Do not take more of it and do not take it more often than your doctor prescribed. To do so may increase the chance of side effects.
Nebido is intended strictly for intramuscular injection (preferably into the buttock). Special care should be taken to avoid injection into a blood vessel The testosterone is gradually released all the time from the reservoir into the bloodstream and remains effective for a very long time.
In bodybuilding stack just as regular testosterone undecanoate (andriol /  restandol) – with other safe dugs like anavar, primobolan, etc. Stacking with stronger drugs like deca will just negate it`s very-low-side-effects advantage.
Benefits of using Nebido
Testosterone replacement therapy can produce profound physical and/or mental changes in patients with low testosterone. The benefits of testosterone replacement on physical and sexual function, energy levels, fat and muscle mass, blood lipids and bone density in men with low testosterone are well accepted. Thus, one should observe following effects with Nebido:
Increased sexual interest generally appears after 3 weeks and levels off at 6 weeks
Increases in erections and sexual satisfaction occur within 6 months
Improvements in quality of life are clear within 3-4 weeks and continue for some time
Improvement in depression or mood is noted after 3-6 weeks and reaches a maximum after 18-30 weeks
Beneficial effects on blood lipids appear after 4 weeks and reach a maximum after 6-12 months
Improvements in blood glucose levels become evident after 3-12 months
Changes in body composition and muscle strength occur within 12-16 weeks and stabilize at 6-12 months
Improvements in bone density show after 6 months and continue for at least 3 years
Minor changes in prostate size and a slight increase in the level of prostate-speciï ¬ �c antigen occur with treatment, leveling off after 12 months. Any further increases may be related to normal aging rather than testosterone treatment.
Source: Onset of effects of testosterone treatment and time span until maximum effects are achieved. Saad F, Aversa A, Isidori AM, et al. Eur J Endocrinol 2011 165(5):675-685.
Nebido might lead to positive results in drug tests. Detection time is longer comparing to oral forms, unfortunately, there is no sufficient information on this subject.
Nebido (testosterone undecanoate) side effects and PCT
Treatment with high doses of testosterone preparations commonly stops or reduces sperm production, although this returns to normal after treatment ceases. High-dosed or long-term administration of testosterone occasionally increases the occurrences of water retention.
Nebido is testosterone ether and androgen-related side effects might be an issue in theory. However, due to mild action these effects are so weak that Nebido could be considered as very safe drug unless the dosage is too high.
However, if you observe any estrogen-related side effects such as breast growth or female-pattern fat deposits start using tamoxifen. If you are toying with high dosages clomiphen might be necessary after the cycle.
If you are diabetic, it may be necessary to adjust your insulin.
Medical usage of Nebido is contraindicated for women and certainly must not be used in pregnant or breast-feeding women. Some exclusions are transsexual females.
Unfortunately, we cannot provide any reliable information on this subject in bodybuilding  so far. Oral testosterone undecanoate is the only form of testosterone, which could be used by females without serious side effects at daily dosage of 120-240 mg, it well combines with anavar (oxandrolone) and, sometimes, primobolan. However, with injectable form of testosterone undecanoate situation is different because more testosterone is delivered into the system (and less wasted) comparing to oral form, so on our opinion, if used by females dosage should be lower than with andriol.
Nebido is not intended for use in women. Nebido is not for use in children and adolescents.
Do not use Nebido:
if you have ever had androgen-dependent cancer or suspected cancer of the prostate or of the breast
if you have or have ever had a liver tumour
Prior to testosterone initiation, all patients must undergo a detailed examination in order to exclude a risk of pre-existing prostatic cancer. Careful and regular monitoring of the prostate gland and breast must be performed (the same is true for any testosterone treatment).
Tell your doctor if you have or have ever had: epilepsy, heart, kidney or liver problems, migraine, temporary interruptions in your breathing during sleep (apnoea), as these may get worse
cancer, as the level of calcium in your blood may need to be tested regularly
blood clotting problems
If you are suffering from severe heart, liver or kidney disease, treatment with Nebido may cause severe complications in the form of water retention in your body sometimes accompanied by (congestive) heart failure.
Missed dose of Testosterone Undecanoate
If you miss a dose of this medicine and your dosing schedule take the missed dose as soon as possible. However, if you do not remember it until the next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Keep out of the reach of children.
Store away from heat and direct light at room temperature.
Keep the medicine from freezing.
Do not keep outdated medicine or medicine no longer needed.