Weekly, twice weekly, or more often?

The total and the split are different questions

Your weekly total is a clinical decision made with your prescriber based on your labs, symptoms and history. Nothing here speaks to what that total should be.

How that total is divided across the week is a separate question, also decided with your prescriber, and it is the one with visible mathematical consequences.

What splitting changes

Dividing the same weekly total across more injections does not change how much you receive in a week. It changes the shape of the curve between injections.

• Fewer, larger injections produce a higher peak after each dose and a lower trough before the next — a more pronounced rise and fall across the week.
• More frequent, smaller injections produce a flatter curve, with peaks and troughs closer together.

How pronounced the difference is depends on the ester. A long ester released slowly from a depot gives a relatively flat curve even on weekly dosing; a short ester produces much more variation across the same interval. The Half-Life Data Table lists the published figures for common esters, and the Half-Life Visualizer lets you compare intervals directly.

Flatter is not automatically better. Whether a flatter curve suits you is a clinical judgement involving your labs, how you feel, and practical considerations like how many injections you are willing to do. That is a conversation with your prescriber.

The arithmetic of a split

Straightforward, and worth getting exactly right because errors here are errors in every injection.

Per-injection dose = weekly total ÷ injections per week.

A 100 mg weekly total split twice weekly is 50 mg per injection. Split every other day — roughly 3.5 times a week — it is about 28.6 mg. That non-round figure is mathematically correct; whether to round it is a protocol question, not a calculation one.

Then convert to a volume and a syringe reading:

Draw volume = per-injection dose ÷ concentration. Oil-based testosterone arrives at a labeled concentration such as 200 mg/mL, so no reconstitution step is involved — you use the label figure directly. Syringe units = draw volume × the syringe's units-per-mL rating.

The TRT Dose Calculator runs this whole chain from a weekly target, and the Split Dose Calculator handles the general case.

Smaller volumes need more care

A practical consequence of splitting more finely: each draw is smaller, and small volumes on a syringe are proportionally harder to read accurately. At 0.15 mL, a misread of a couple of units is a much larger percentage error than the same misread at 0.5 mL. Matching your syringe size to your typical draw volume helps considerably.

What to track either way

• Every injection with its date and site. Frequency only means anything if the actual intervals are recorded.
• Your concentration. From the vial label — everything downstream depends on it.
• Labs, with the timing relative to your last injection. This is the detail most often omitted and most often needed: a trough level and a peak level are very different numbers, and a lab result without its timing is hard to interpret.
• How you feel across the week, if a pattern is what you and your prescriber are trying to see.

The Free Testosterone Calculator estimates free and bioavailable testosterone from total T, SHBG and albumin using the Vermeulen equation, which is useful context when total T alone does not explain what you are seeing.

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