Deca: Therapeutic Benefits

Following the most recent template PEDsR posts have been using, I’ve split out the studies into their own section. In this case, there’s a total of 5 (two are very similar and are marked as 2a and 2b respectively), due to the diverse interest in deca and variation in outcomes examined. I know that reading study abstracts can be a grind, and readers can skip past it if they wish as I further summarize the key learnings from the studies. That said, reading the abstracts are an excellent way to make your own conclusions about the compound. Any feedback on formatting from the brommunity is welcome and appreciated.


Deca-durabolin, aka deca, aka nandrolone decanoate, is an AAS still used medically for the treatment of anemia and osteoporosis. It is mildly estrogenic and slightly more anabolic than test (note, I couldn’t find data to support this claim, but multiple studies claim the same thing without actually providing the anabolic or androgenic rating, so we’ll assume it is accurate). It tends to have two main PED uses - off-season bulking, and low dose therapy. Naturally, the clinical data we have is on the latter.


Study 1: 29 patients on dialysis were selected for a trial where deca was used to improve malnutrition, muscle atrophy and fatigue. 14 patients received 100mg once a week for 6 months, while 15 received a placebo. The group receiving deca improved LBM by 2.6kg compared to placebo, creatinine went up (indicating increase in muscle mass), and time to complete walking and stair-climbing test decreased from 36.5 to 32.7 seconds. This is compared to placebo where the time taken increased from 38.7 to 42.1 seconds. There were no significant adverse reactions, with injection site irritation and acne the only effects reported.

Study 2a: 17 HIV+ patients who had lost 5-15% of body weight received 100mg every 2 weeks for 16 weeks. Body weight and lean body mass (3kg) increased significantly, as well as improving quality of life (blood, liver and kidney markers). There were no adverse effects, and no toxicity. Subjective patient feedback indicated dramatic improvements in feeling of well being, physical function and energy.

Study 2b: similar to 2a. 21 days, with 4 on a 65mg/week and 7 on 200mg week. What is most notable about this study is the listing of nitrogen balance, with both doses resulting in 33-52g nitrogen/14 days (0.5-0.9kg lean tissue / week), compared to control of loss of 11g nitrogen/week. Normal nitrogen balance levels range between 6-17g.

Study 3: 28 health males participated in a progressive overload training program, and received 1mg/kg every 2 weeks. There was no change to body composition or strength.

Study 4: 32 rats were dosed with 5/mg kg twice a week for six weeks, which has a human equivalent dose of roughly 1.6mg/kg (150mg for a 90kg male). Testosterone was significantly suppressed in comparison to control. Muscle growth was specific to the rats calf (soleus) and was about 33% greater than control.

Not studied in clinical trials on humans, but studied on animals, is the effect that deca has on joint pain. Broscience has known this for some time, and this was validated in 2011 in a study on rabbits. During the 6 week recovery, the rabbits given deca had less impairment of the tendon, which matches our anecdotes/brodotes.


In post-menopausal women, it is dosed at 25-50mg once every 6-12 weeks for androgen replacement or 50mg every 2-4 weeks for osteoporosis. In kids for treatment of anemia it’s 25-50mg every 3-4 weeks. While we’re not exactly looking at old women or children for guidance on doses, it is indicative of the therapeutic benefit.

Broscience has it that deca bulks will usually start at around 400mg per week, paired with a relatively high dose of test to preserve sexual function. I don’t agree with this rationale, and if paired with testosterone, test should be at far lower levels, <100mg. This would be due to the higher binding affinity of DHT (testosterone) displacing DHN (nandrolone). A bulking dose of 300-400mg does seem appropriate though, coupled with 50-100mg of testosterone. For therapeutic use, 50-150mg would be effective. Keep in mind the long ester, the 6-12 day half-life and that its effects last 2-3 weeks post injection, and set your expectations appropriately i.e. it is unlikely to provide immediate benefit, and will take 4-5 weeks before relief is experienced.

Side effects

DHT has anti-anxiety properties, and is derived from testosterone. Unfortunately, deca (and any nor, looking at you tren), does not reduce into DHT, but reduces to DHN. This can elevate anxiety. However, the plus side of this is that it has a reduced impact to your hairline, for reasons which we’ve covered several times recently (tren, RU58841, hair loss)., my old stomping ground, claims that combining a nandrolone hormone with a 5-alpha reductase inhibitor, like finasteride, will enhance androgenicity and increase hair loss. It’s been broscience for generations, but I’m skeptical of the claims. While it is certainly true that finasteride will prevent the conversion of deca into DHN, binding strongly with the androgen receptor and activating the AR fully does not necessarily equal hair loss, and given the lack of DHT I simply don’t see how this interaction increases hair loss. If I’m misinformed please let me know, and I will correct my stance.

When running (heh) deca, cardio does not seem to lower blood pressure, improve ventricular hypertrophy, or arterial health. Some studies show that it increases cardiac hypertrophy (no surprise there), elevates blood pressure, and has an impact on lipids. Your diet, therefore, must be on point when running deca since this is the only way to minimize increases in blood pressure outside of prescription meds.

Prolactin is often thought to be of concern when running deca, and as we know from our article on tren this is due to nandrolone binding to the progesterone receptor with about 22% the affinity of progesterone - any increase in progesterone is usually very noticeable. I also saw a very interesting and well written opinion piece that argues that deca aromatizes in a complex way and that the rise in e2 is enough to explain gyno. Whatever the culprit, I would urge you to dial in your AI and B6/caber while on any nor cycle through the use of blood work on-cycle, paying attention that neither are high nor low, but are within range and at a normal ratio.

At doses of 20mg/kg in rats, there is an attenuation on serotonin, leading to increased aggression. In fact, deca seems to have a highly complex relationship on the mental health of subjects, impacting not only aggression, but anxiety, fear, stress, can enhance the reward effects of stimulants/amphetamines, and decrease cognitive function. 20mg/kg is a human equivalent dose of just shy of 300mg week.

Key Learnings

The most frequent use of deca is osteoporosis and anemia, and it has been used for many other situations requiring physical recovery of the patient. Low dose deca evidently offers significant benefits to those who are catabolic (due to disease or otherwise), and can improve blood markers. However, for muscle hypertrophy you can see from Study 3 that low dose really is not going to cause any increase in strength or size. Study 4 shows it is possible, however, but the dose will need to be at least 150mg-200mg, and preferably 300mg or more.

Note that these studies did not utilize testosterone alongside deca, indicating that it might be used for monotherapy at low doses but keep in mind this may have been due to the patients (hiv and wasting away). It was exceptionally well tolerated, no significant adverse events, though higher doses are likely a very different story. The lack of DHT conversion will mean that some users experience ED, and is the reason we so often see deca paired with high levels of test.

Frankly, low dose deca seems incredibly appealing given its impact on nitrogen retention and its positive effects on kidney, liver and joints. The latter is exactly why I’m utilizing it currently. I have seen some brodoses of 800mg and more of deca, and to that I think the user is just asking for issues that come from the binding of DHN in tissues that really ought to be binding with DHT.

Shoutout to /u/Sean0987 who requested deca-durabolin to be covered.