Two administrations of 0.5 mg instead of one of 1 mg — the same 1 mg a week either way. Total weekly exposure is unchanged; what changes is the peak-to-trough ratio, and for an agent with a half-life measured in days the trough barely moves because the dosing interval is already short relative to it. The arithmetic is the easy part: 1 ÷ 2 = 0.5. Whether it is worth doing is a pharmacokinetic question, and nothing here is medical advice.
Start with the half-life. For an agent with a one-week half-life, weekly dosing already produces a nearly flat profile and splitting changes very little.
Splitting that same weekly dose into two half-doses at 3.5-day intervals gives τ/t½ = 0.5 and a peak-to-trough ratio of about 1.41. The profile is flatter, and the difference between a 2-fold and a 1.4-fold swing is not obviously perceptible.
Dead space by syringe type
| Configuration | Dead volume | Loss at 5 mg/mL | Over 20 draws |
|---|
| Fixed-needle insulin syringe | 3–5 µL | 15–25 µg | 0.3–0.5 mg |
| Low-dead-space, detachable | <2 µL | <10 µg | <0.2 mg |
| Standard luer-lock + 30G | 35–60 µL | 175–300 µg | 3.5–6 mg |
| Luer-lock + 21G drawing needle | 70–100 µL | 350–500 µg | 7–10 mg |
Concretely, halving a dose accurately requires the reading resolution to support it. A 10-unit dose split into two 5-unit doses is at the coarse end of any barrel.
Published half-lives for the agents in this class range from about thirteen hours to about a week, which is the range over which the answer changes.
More injections means more handling risk, and that cost is certain while the benefit is not.
If you cannot read half the dose accurately, you cannot split it accurately.
Small correction: the units in the third paragraph should be micrograms, not milligrams. – rhian_prydderch 6 months ago 2Adding that a fixed-needle syringe loses about a tenth of what a luer one does. – Dr_Nadia_Farsi 7 months ago add a comment