Common (>10% users at bodybuilder doses):

• Atherogenic lipid changes — HDL drops 30-50%, LDL/ApoB rises. Worse on the lipid dimension than aromatizing AAS because the lack of estradiol means no E2-mediated HDL preservation. DHT-class compounds are particularly bad for HDL — drostanolone is at the worse end of the spectrum here.
• HPG axis suppression — less than testosterone monotherapy at equivalent doses, not zero. LH/FSH drop within weeks, endogenous T reduced. Recovery 4-8 weeks post-cycle with PCT.
• Accelerated androgenic alopecia in genetically predisposed users. Drostanolone is a potent peripheral androgen (DHT-class with 3α-HSD blocking) — for users with shorter AR CAG repeats and male-pattern baldness predisposition, this is one of the more aggressive AAS for hair loss.
• Acne / oily skin in susceptible users — DHT-class AR activation at sebaceous glands.
• Mild aggression / irritability / drive elevation (DHT-class CNS effects).

Less common (1-10%):

• Hematocrit elevation (red blood cell mass increase) — modest, less than testosterone esters.
• Mild blood pressure elevation — less than testosterone or trenbolone.
• Sleep disturbance in some users.
• Libido shifts (initially up, later down as HPG suppression takes hold).
• Mild prostate hypertrophy effects in older users — less relevant for 20yo.
• Forearm / bicep "pumps" — transient, dehydration-related, typical of DHT-derived AAS.
• Injection site reactions — pain, mild inflammation, particularly with enanthate ester (lower carrier oil-to-active ratio than propionate but enanthate-specific UGL formulations vary widely in injection comfort).

Rare-serious (<1% but worth knowing):

• Severe atherogenic dyslipidemia leading to accelerated CVD with cumulative multi-cycle use over years — comparable to other DHT-class AAS profiles, possibly worse on HDL specifically.
• Cardiomyopathy — extrapolated from broader AAS literature (Baggish et al. cardiac MRI studies); cumulative exposure-dependent; drostanolone-specific cardiac data is sparse.
• Persistent post-cycle hypogonadism — documented in young AAS users with otherwise healthy HPG axes; risk likely higher when HPG axis is still maturing (late teens / early 20s). This is the core SKIP-AT-20 mechanism.
• Severe androgenic alopecia / accelerated male-pattern baldness in predisposed users — can be irreversible.
• Mood disorder triggering — supraphysiologic AR exposure during prefrontal maturation; case reports exist across AAS class, drostanolone-specific data sparse.

Specific watch periods:

• At age 20: HPG axis is still consolidating final adult set-point. Suppression at this age has higher theoretical risk of permanent change vs same suppression at 30. This is the core SKIP-AT-20 mechanism, applies to drostanolone same as other AAS.
• Week 4 of any cycle: ALT/AST + lipid panel — flag if HDL drops >50% or BP >140/90.
• End of cycle: Full HPG panel (T, LH, FSH, E2, DHT) to quantify suppression.
• Week 4-8 post-cycle: HPG recovery check; if still suppressed, formal PCT or endocrinology consult.