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Deca Durabolin is the best-known brand name for nandrolone decanoate, an injectable anabolic steroid bodybuilders have used for decades to add size in the off-season. In a typical Deca cycle, users report 300 to 600mg a week for 12 weeks or longer, almost always on top of testosterone. Deca is known for steady, full-looking gains and joint comfort, and just as well known for a side effect with its own nickname: deca dick.
This guide covers how Deca cycles are commonly run, realistic results, the side effects that matter and what actually causes deca dick. Nothing here is a recommendation to use it. Nandrolone is a controlled substance in the US and many other countries, and much black-market Deca is not what the label says.
Key Takeaways
- Deca is nandrolone decanoate, a slow-acting injectable steroid. Users commonly report 300-600mg a week for 12-16 weeks, almost always with testosterone. These are user figures, not clinical doses.
- Deca dick (erectile dysfunction and low libido on a cycle) is mainly a low-androgen problem: Deca shuts down natural testosterone and is converted to a weaker androgen, DHN, instead of DHT.
- High prolactin is often blamed, but it is only one possible cause. Cabergoline only makes sense when a blood test shows prolactin is actually high.
- Deca is not a beginner or “organ-friendly” steroid. It strongly suppresses testosterone, lowers HDL cholesterol, raises red blood cell counts and can cause water retention and gyno.
- In a 2023 study of 641 men who had stopped anabolic steroids, only 48% had fully recovered their hormone levels.
What Is Deca Durabolin?
Deca Durabolin is nandrolone decanoate, the decanoate ester of nandrolone (19-nortestosterone). Nandrolone is testosterone with one carbon atom removed, a small change that gives it a strong effect on muscle relative to the skin, scalp and prostate. Organon introduced Deca-Durabolin in the early 1960s.
Doctors have prescribed nandrolone for anemia caused by kidney failure and, in some countries, postmenopausal osteoporosis. It comes in two common forms:
- Nandrolone decanoate (Deca): A long ester with a half-life of roughly one to two weeks, usually injected once or twice a week. It builds and clears slowly.
- Nandrolone phenylpropionate (NPP): A short ester, commonly injected every two to three days. It clears faster, so side effects fade sooner after stopping.
How Nandrolone Works
Nandrolone binds the androgen receptor, raising muscle protein synthesis and nitrogen retention. Three other properties shape how a Deca cycle feels:
- It turns into a weaker androgen. The enzyme 5-alpha reductase converts testosterone into DHT, a stronger androgen. The same enzyme converts nandrolone into dihydronandrolone (DHN), which binds the androgen receptor more weakly than nandrolone itself. That is why Deca causes less acne and hair loss than many steroids, and part of why it causes deca dick.
- It converts to estrogen, but less than testosterone does. Its aromatization rate is commonly cited as about 20% of testosterone’s. In a stack, most estrogen comes from the testosterone.
- It acts on the progesterone receptor. This progestogenic activity is widely thought to add to water retention and gyno risk.
Deca Durabolin Cycle: What Users Report
The cycles below are based on user reports and coaching literature. They are not clinical doses or recommendations, and no controlled study has tested nandrolone at these doses in healthy men.
Almost every reported Deca cycle includes testosterone, because nandrolone shuts down natural testosterone and, as a weak androgen in many tissues, cannot replace it. Deca-only cycles are where users most often report low libido, erection problems, fatigue and low mood, typically from around weeks 3 to 4 at 400mg a week or more.
Commonly Reported Test and Deca Cycle (12 Weeks)
| Weeks | Testosterone Enanthate | Nandrolone Decanoate |
|---|---|---|
| 1-12 | 300-500mg/week | 300-400mg/week |
This is the classic Test and Deca bulking cycle, most often described as a first Deca cycle for men who have already run a testosterone-only cycle. Many users keep the testosterone dose equal to or higher than the Deca dose to limit libido problems, a forum rule of thumb that has never been tested.
Commonly Reported Test, Deca and Dianabol Cycle (14 Weeks)
| Weeks | Dianabol | Testosterone Enanthate | Nandrolone Decanoate |
|---|---|---|---|
| 1-4 | 20-30mg/day | 500mg/week | 400mg/week |
| 5-14 | None | 500mg/week | 400mg/week |
Because Deca builds slowly, some users add Dianabol for the first four weeks for faster early gains. Dianabol is 17-alpha-alkylated, so it adds liver strain, higher blood pressure and more water retention, and every extra compound lowers the odds of a full hormonal recovery. For how nandrolone compares with trenbolone in a bulk, see our Deca vs Tren comparison.
Low-Dose Deca on TRT
Some men on testosterone replacement therapy report adding 100-200mg of Deca a week, mainly for joint comfort. It is still a second anabolic steroid, with the same effects on cholesterol, red blood cells and fertility.
Deca Durabolin Dosage: Clinical vs Reported
Medical and bodybuilding doses are far apart:
| Use | Dose | Source |
|---|---|---|
| Anemia of kidney failure, men | 100-200mg/week | US prescribing information |
| Anemia of kidney failure, women | 50-100mg/week | US prescribing information |
| Postmenopausal osteoporosis | 50mg every 3 weeks | Prescribing information in some countries |
| Bodybuilding, entry level | 300-400mg/week | User reports |
| Bodybuilding, intermediate | 400-600mg/week | User reports |
| Bodybuilding, advanced | 600-800mg/week | User reports |
Higher doses do not bring proportionally better results, while reports of water retention, high blood pressure, high red cell counts and sexual side effects climb with dose. Women face a high risk of masculinizing effects, some of which, such as a deeper voice, can be permanent.
Deca Durabolin Results: What to Expect
Deca is slow. Users report little in the first two to three weeks, visible changes by weeks 4 to 6 and the full effect from week 8 onward. These timelines come from user reports, not trials.
Commonly Reported Results
- Size and fullness: Steady weight gain with a full, thick look. Part of that fullness is water and glycogen.
- Strength: Usually climbs through the cycle, especially on compound lifts.
- Appetite: A bigger appetite is commonly reported, which helps a bulk and works against a cut.
What the Research Shows
No trial has tested Test and Deca at bodybuilding doses, but clinical studies give a sense of scale. In a randomized trial in dialysis patients, 100mg of nandrolone decanoate a week for six months increased lean body mass compared with placebo. In the best-known testosterone trial (Bhasin and colleagues, 1996), healthy men who took 600mg of testosterone enanthate a week for 10 weeks and lifted weights gained about 6kg of fat-free mass. Men who lifted on placebo gained about 2kg.
Claims of 30lbs of lean muscle from a first cycle are not supported. Much of the weight gained on a bulk is water, glycogen and fat, and some muscle is lost after the cycle as hormone levels fall.
Deca Durabolin Side Effects
Deca is often called a “mild” or even “healthy” steroid because it is easy on the liver and causes less hair loss than many steroids. That does not make it safe. Drugs.com lists the Deca-Durabolin side effects seen in medical use, at doses far below what bodybuilders report.
Testosterone Suppression and Fertility
Nandrolone is strongly suppressive, even at modest doses. It shuts down LH and FSH, the hormones that tell the testes to make testosterone and sperm, so smaller testes, low sperm counts and low natural testosterone are expected.
Recovery is not guaranteed. In a 2023 study of 641 men seen at a UK clinic after stopping anabolic steroids, only 48% had fully recovered their reproductive hormones (LH, FSH and testosterone back in the normal range). Men who had used more compounds were less likely to recover.
Cholesterol, Blood Pressure and the Heart
Like other anabolic steroids, nandrolone lowers HDL (“good”) cholesterol, though usually less than oral steroids, and water retention can raise blood pressure. A 2017 American Heart Association scientific statement linked anabolic steroid use to heart muscle damage and faster artery disease.
Red Blood Cells
Nandrolone raises red blood cell production, which is why doctors used it for anemia. In healthy men it can push hematocrit too high, thickening the blood and raising the risk of clots: a risk to monitor, not a performance benefit.
Water Retention and Gyno
Deca is often said to cause little water retention, but bloating is one of its most commonly reported side effects, especially at higher doses. Its estrogenic and progestogenic activity and the testosterone it is stacked with both contribute, and also make gynecomastia (breast tissue growth) possible.
Joints: What Is Real
Users often say Deca “lubricates the joints,” and many report less joint pain. Nandrolone does increase bone mineral density, which is why it has been used for osteoporosis, and animal studies suggest it affects collagen in connective tissue. But no good human trials show it protects or repairs joints, and doctors do not prescribe it for joint pain.
Liver, Mood and Other Effects
Injectable nandrolone is not 17-alpha-alkylated, so its liver strain is low compared with oral steroids such as Anadrol or Dianabol. Its main risks are hormonal and cardiovascular. Users also report low mood, lethargy and night sweats, and acne and hair loss are possible.
Deca Dick: Why Deca Causes Erectile Dysfunction
Deca dick is slang for erectile dysfunction and low libido during or after a nandrolone cycle. It is reported more often with Deca than with most other steroids, and often earlier in the cycle.
What Causes Deca Dick?
The most likely cause is low androgen activity in the places that matter for sexual function. Three things combine:
- Natural testosterone shuts down. Testosterone is a key driver of libido and erection quality (see the Cleveland Clinic’s overview of testosterone).
- DHT falls. With natural testosterone shut down, the body makes less DHT, and nandrolone is converted to the weaker DHN instead. Animal studies show androgens help maintain nitric oxide production in penile tissue, which erections depend on.
- Hormone balance shifts. High estrogen and, in some users, high prolactin can suppress libido further.
Prolactin gets most of the blame online. Very high prolactin does suppress libido and testosterone production, and estrogen can raise prolactin. But controlled evidence that nandrolone itself reliably raises prolactin is thin. It is one possible cause, not the cause, and only a blood test can tell.
How Long Does Deca Dick Last?
Reports range from a few weeks to several months. On cycle, symptoms often ease when the testosterone dose is adjusted or Deca is stopped. After a cycle, they tend to last until natural testosterone recovers, which is slow because Deca clears slowly.
If erections and libido have not returned within a few months of stopping, natural testosterone production has usually not recovered. That is a medical condition (anabolic steroid-induced hypogonadism) worth seeing a doctor about.
How Users Try to Prevent It
There is no proven way to prevent deca dick other than not using nandrolone. Users commonly report:
- Running Deca with a testosterone base, often at a dose equal to or higher than the Deca dose
- Keeping the Deca dose moderate, since reports climb at 400mg a week and above
- Using NPP instead of Deca, so the drug clears in days rather than weeks if problems start
- Testing testosterone, estradiol and prolactin before reaching for another drug
- Using ED drugs such as sildenafil, which help blood flow but do not fix the hormone problem behind it
Cabergoline (Dostinex) and Deca
Dostinex (cabergoline) is a prescription dopamine agonist approved to treat hyperprolactinemia, a condition in which the body makes too much prolactin. Steroid users often take cabergoline during Deca cycles to keep prolactin down.
It only makes sense if prolactin is actually high. Without a blood test, it treats a problem that may not exist, and it does nothing for deca dick caused by low androgen levels.
For hyperprolactinemia, the prescribing information starts at 0.25mg twice a week, and users report similar doses on a cycle. Side effects include nausea, dizziness, headache and low blood pressure. At the much higher doses once used for Parkinson’s disease, cabergoline was linked to heart valve damage.
PCT After a Deca Cycle
Post-cycle therapy (PCT) means taking clomiphene (Clomid) or tamoxifen (Nolvadex) after a cycle to restart natural testosterone production. Neither drug is approved for this use.
Because Deca clears slowly, users commonly report starting PCT two to three weeks after the last injection. The most commonly reported protocols are:
| PCT Drug | Commonly Reported Protocol | Duration |
|---|---|---|
| Clomiphene (Clomid) | 50mg/day weeks 1-2, 25mg/day weeks 3-4 | 4 weeks |
| Tamoxifen (Nolvadex) | 40mg/day weeks 1-2, 20mg/day weeks 3-4 | 4 weeks |
SERMs & AIs
Overview
- Form: Oral capsules (25 mg each, 60 capsules)
- Researched Dosage: 25 mg to 50 mg daily for PCT
- Typical Cycle: 4-6 weeks
- Cost: $69.95
- Stacking Options: Tamoxifen, HCG, Enclomiphene
Pros
- A SERM that blocks estrogen at the hypothalamus, prompting the body to make more LH, FSH and its own testosterone.
- Studies in men with low testosterone found it raised testosterone while preserving sperm production, unlike TRT.
- It is oral, inexpensive and has been in medical use since 1967, so its effects are well documented.
Cons
- About a third of each dose is zuclomiphene, a long-lasting isomer linked to mood swings, irritability and low mood.
- Blurred vision, floaters and light sensitivity have been reported; visual symptoms are a reason to stop.
- It is FDA-approved only for female infertility, so use in men is off-label, and this product is sold for research use only.
Clomid or Nolvadex After Deca?
An old claim, which this page used to repeat, says Nolvadex should be avoided after Deca because it raises progesterone and prolactin and worsens gyno. There is no good evidence for this: tamoxifen is not known to raise prolactin, and both drugs are commonly reported after nandrolone cycles. Clomiphene is more often linked to mood swings and visual disturbances, tamoxifen to hot flashes and, rarely, blood clots.
SERMs & AIs
Overview
- Form: Oral Capsules
- Dosage: 25-40 mg daily for PCT or for gyno flare-ups
- Typical Cycle: 4-6 weeks
- Cost: $81.95
- Stacking Options: Higher testosterone doses or post-cycle recovery
Pros
- Large mortality benefit in ER-positive breast cancer; five years of adjuvant treatment cuts recurrence roughly by half and breast cancer mortality by about a third, with the effect persisting well past the treatment period
- Works in premenopausal and postmenopausal women alike, unlike aromatase inhibitors, which makes it the default for younger patients
- Bone-protective in postmenopausal women, since it acts as a partial estrogen agonist in bone — the reverse of anastrozole's main liability
Cons
- Endometrial hyperplasia and a two-to-three-fold increase in endometrial cancer risk in postmenopausal women, requiring investigation of any abnormal bleeding
- Elevated risk of venous thromboembolism and pulmonary embolism, particularly around surgery or immobility
- Hot flashes, vasomotor symptoms and mood effects are common; CYP2D6 status and strong inhibitors such as certain SSRIs can reduce conversion to the active metabolite
PCT does not guarantee recovery. In the 2023 study of 641 men, PCT was linked to faster short-term recovery, but the authors did not recommend it and called for proper research. Blood work before the cycle and after PCT is the only way to know where recovery stands. Our PCT guide covers recovery in more depth.
Legality, Drug Testing and Counterfeits
United States: Nandrolone is a Schedule III controlled substance. Possessing it without a prescription is a federal offense, and selling it carries heavier penalties.
Elsewhere: Rules vary. In the UK, anabolic steroids are Class C drugs. Possession for personal use is not an offense, but supply, and importing by post or courier, are illegal.
Sport: Nandrolone is on the WADA Prohibited List at all times, in and out of competition. Its metabolites can be detected in urine for months after the last Deca injection.
Counterfeit Risk
A 2022 meta-analysis pooled 19 studies covering 5,413 black-market steroid samples. On average, 36% were counterfeit (wrong or missing active ingredient) and another 37% were substandard (wrong dose or contaminated). A vial labeled Deca may hold a different steroid, the wrong dose or something non-sterile.
The Bottom Line
Deca Durabolin builds size and strength steadily, but it is not the gentle beginner steroid it is often sold as. It shuts down testosterone hard, and deca dick is a predictable result of that, not bad luck.
- Reported cycles almost always pair 300-600mg of Deca a week with testosterone. These are user figures, not tested doses, and side effects climb with dose.
- Deca dick comes mainly from low androgen activity. Prolactin is only sometimes involved, so cabergoline only makes sense when a blood test shows prolactin is high.
- Recovery after a cycle is slow and not guaranteed, and much black-market Deca is counterfeit or underdosed. Blood work before and after is the only way to know where you stand.
Frequently Asked Questions
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