Primobolan is widely held in high regard as one of the few anabolic steroids that is considered very ‘mild’ in the sense that it presents absolutely zero risk of any Estrogenic side effects at any dose as well as its very weak androgenic strength rating, which allows it to exhibit far less severity in terms of the potential of androgenic side effects than most other anabolic steroids. This is the reason as to why Primobolan is often pitted against and compared to its close brother, Anavar. Both are anabolic steroids that have been utilized medically in the treatment of women and children with very little risk of ill effects and both are considered very ‘mild’ in regards to potential side effects. This is, however, where the similarities between the two end, as Primobolan is an anabolic steroid that possesses not only a weak affinity for various side effects, but also a weak anabolic strength when compared to the majority of other anabolic steroids in existence (and in comparison to Anavar).
Estrogenic Side Effects
Primobolan is a DHT-derivative anabolic steroid, which means it does not exhibit any interaction with the aromatase enzyme at any dose, and therefore Primobolan side effects are completely void of any Estrogenic side effects. Estrogen-related side effects such as water retention, rising blood pressure (as a result of water retention) and gynecomastia are nonexistent from Primobolan alone.
Androgenic Side Effects
Although Primobolan possesses a very low androgenic strength rating in comparison to Testosterone, Primobolan might still exhibit androgenic side effects especially in individuals with a greater sensitivity to this category of Primobolan side effects. All anabolic steroids exhibit androgenic effects to varying degrees, and some less than others. Primobolan is one such anabolic steroid in which it tends to exhibit far less androgenic activity than other anabolic steroids, but the risk of androgenic side effects presenting themselves should never be completely ignored with Primobolan. Androgenic side effects include the following: increased sebum secretion (oily skin), increased bouts of acne (linked to increased sebum secretion), bodily and facial hair growth, and the increased risk of triggering Male Pattern Baldness (MPB) in individuals that possess the genetic trait required for the condition to manifest itself. Primobolan side effects in the realm of androgenic side effects also include virilization effects in female users. Virilization effects in females can include the development of male secondary sex characteristics (deepening of the voice, growth of body and facial hair), clitoral enlargement, and menstrual irregularities. Primobolan in particular should not aggravate these conditions if female doses are kept sensible and cycle lengths are kept short and moderate. One particular advantage to Primobolan (and all DHT-derivatives in particular) is the fact that Primobolan does not interact with the 5-Alpha Reductase enzyme (the enzyme responsible for the conversion of Testosterone to the much more androgenic Dihydrotestosterone), and so therefore there is no risk involved in Primobolan converting into any stronger androgens from such a process. It can be safe to assume then that the androgenic strength associated with Primobolan should remain constant and consistent throughout use.
HPTA and Endogenous Testosterone Production Side Effects
When utilized at doses necessary for the purpose of performance and physique enhancement, all anabolic steroids will cause either suppression or total shut down of the HPTA (Hypothalamic Pituitary Testicular Axis) and endogenous natural Testosterone production through the negative feedback loop. Primobolan side effects are no exception to this rule for all anabolic steroids. Primobolan in particular is always commonly touted as being an anabolic steroid that is ‘mild’ in its Testosterone suppression side effects. This is quite obviously a very false rumor that must be cleared up, as clinical data has demonstrated. Primobolan, when administered in medically prescribed doses (approximately 20 – 25mg per day) has shown to cause very minor suppression of the HPTA. However, this is not the case when bodybuilding doses and doses necessary for physique and performance enhancement are brought into consideration. For example, one study administered 30 – 45mg per day of oral Primobolan to test subjects in which over half of these subjects exhibited a 15 – 65% suppression of endogenous Testosterone production. The dose administered to these subjects is a dose that is actually considered still fairly low (30 – 45mg per day) for performance and physique enhancing purposes. Considering that bodybuilding and performance enhancing doses for Primobolan typically start in the 100mg range, Primobolan very well does exhibit some strong suppression of endogenous Testosterone production. Although the level of suppression resultant from Primobolan is lower than most anabolic steroids, it still presents itself as quite a suppressive compound, and many individuals must be aware of this.
It is very important that following any cycle, each individual engages in a proper and well-structured and planned Post Cycle Therapy (PCT) program, which includes the use of Testosterone-stimulating compounds (such as Nolvadex and/or HCG) for a 4-6 week period immediately after the end of any cycle in order to ensure full restoration of the body’s endogenous production of Testosterone and related hormones. Without a proper PCT program, the user risks damaging and/or shutting down their HPTA for the duration of life, at which point medical intervention will be necessary.
Hepatotoxic Side Effects
Injectable Primobolan (Methenolone Enanthate) as well as oral Primobolan (Methenolone Acetate) are both void of the typical C17-alpha alkylation common in nearly all oral anabolic steroids, and therefore Primobolan presents no measurable hepatotoxic effects on the body. Oral Primobolan has failed to demonstrate any changes in liver enzyme values that would be cause for concern. Primobolan in particular does possess in its own right a resistance to hepatic metabolism and breakdown, and only one incidence of a death resultant of hepatotoxicity and liver failure from oral Primobolan has been recorded in one male elderly individual who was prescribed the compound for the purpose of treating anemia. Therefore, higher doses of oral Primobolan can indeed be utilized but it must be noted that oral Primobolan does still possess a measure of resistance to metabolism and breakdown in the liver, and therefore the risk of hepatotoxicity from Primobolan must not be completely ignored, especially as doses of the oral format are increased to higher and higher amounts.
The injectable Primobolan (Methenolone Enanthate) is void of any liver toxicity issues, as its route of administration bypasses the first pass through the liver.
Cardiovascular Side Effects
Primobolan side effects include that of cardiovascular strain and negative cholesterol changes, which is a side effect shared among all anabolic steroids. This involves the reduction of HDL (the good cholesterol) and increases of LDL (the bad cholesterol). The result of such changes is an increased risk of arteriosclerosis, and the degree to which these changes occur for the worse are usually dose-dependent (with higher doses increasing the negative changes and the risks). Other factors that affect these negative cholesterol changes are: duration of use, and route of administration. In terms of the route of administration, oral anabolic steroids are known as being the worst for their negative impacts on cholesterol in comparison to injectable anabolic steroids. This is where oral anabolic steroids hold a negative reputation for exhibiting a far worse negative impact on cholesterol in comparison to injectable anabolic steroids. This is due to the fact that the liver is essentially the body’s cholesterol processing and production center, and increased hepatotoxicity as a result of oral anabolic steroid use is associated with negative cholesterol changes.
Proper attention to a clean diet and the inclusion of various healthy cholesterol promoting foods (such as omega-3 fatty acids and fish oils (at least 2 – 4 grams per day) is essential while on a cycle of anabolic steroids.
 Proc. Intern. Congr. Hormonal Steroids, Milan, 1962. Excerpta Med. Intern. Congr. Ser No. 51, p. 209. Excerpta. Med. Found., Amsterdam, 1962.
 Comparative studies about the influence of metenolone acetate and mesterolone on hypophysis and male gonads. Trenkner R, Senge T, Hienz H et al. Arzneimittelforschung. 1970 20(4):545-7.
 Failure of non-17-alkylated anabolic steroids to produce abnormal liver function tests. J Clin Endocrinol Metab. 1964 Dec;24:1334-6.