TRT Split Protocols Explained: Daily vs E3.5D vs Weekly

Most TRT protocols start with a weekly intramuscular injection. After bloodwork, many lifters end up splitting that dose into smaller, more frequent injections. This post explains why splitting works, the most common protocols, and the SubQ vs IM debate.

Why split your dose?

Testosterone Cypionate has a half-life of around 8 days. With a weekly injection, your testosterone level peaks roughly 24-48 hours after the shot, then decays steadily until your next dose. The peak is high (often supraphysiological) and the trough is low (sometimes back near baseline by day 7).

These hormonal swings drive symptoms: high estrogen conversion at peak (water retention, mood swings, gyno risk), low energy and libido at trough. Splitting the dose into smaller, more frequent injections flattens this curve — more stable T, less E2 conversion, fewer side effects.

Common protocols

Weekly (1×/week)

Typical: 100-200 mg Test Cyp IM. Pros: One injection per week. Cons: Highest peak-trough swings, most E2 sides.

E3.5D (twice weekly, every 3.5 days)

Typical: 50-100 mg Test Cyp IM, Monday morning + Thursday evening. Pros: Smoother levels, fewer sides. Cons: Two injections per week.

E2D (every 2 days)

Typical: 30-60 mg SubQ. Pros: Very stable levels. Cons: 3-4 injections per week.

Daily microdose

Typical: 15-25 mg SubQ daily. Pros: Most stable T levels possible, lowest E2 conversion (small frequent doses don't aromatise as much), often eliminates the need for an AI. Cons: Daily injection commitment.

SubQ vs IM

Subcutaneous injection (into the fat layer) was historically considered inferior to intramuscular but research has shown it produces equivalent serum testosterone levels with several practical advantages:

• Less painful — small insulin syringe vs IM needle
• More site rotation options — abdomen, thighs, glutes, delts
• Slower release — flatter peaks
• Easier to self-administer — no need for muscle, just pinch fat

Most modern TRT protocols, especially daily microdose, use SubQ with a 27-31 gauge insulin syringe.

Site rotation

Repeated injections in the same site cause scar tissue (lipoatrophy or fibrosis) over time. Rotate across at least 4-6 sites and don't pin the same exact spot more than once per fortnight.

Common SubQ sites: left/right abdomen, left/right thigh, left/right glute, left/right delt. LFTD's site rotation tracker suggests the next site based on longest rest.

Bloodwork drives the protocol

Don't pick a protocol and stick to it forever. Get bloodwork at 6-8 weeks after starting or any dose change. Look at:

• Total Testosterone — usually targeted 600-900 ng/dL trough
• Free Testosterone — the bioavailable fraction
• Estradiol (sensitive) — typically 20-40 pg/mL
• SHBG — high SHBG suggests less frequent dosing, low SHBG suggests more frequent
• Hematocrit — >52% needs dose reduction or therapeutic phlebotomy

Track everything

LFTD's protocol tracker logs every pin, calculates your compliance %, suggests rotation sites, and overlays your TRT timeline on every workout chart so you can see exactly when your bench started moving up after dose changes.