⚠ Contaminated BAC water from Amazon seller — need advice

Answering the narrow version, because the broad one does not have a single answer. Do it in two steps and it stops being confusing. First concentration: 10mg into 2ml is 5mg/ml. Then volume: a 0.5mg dose is 0.5 ÷ 5 = 0.1ml. Then units, and this is where people go wrong — a U-100 syringe is graduated in hundredths of a millilitre, so 0.1ml is 10 units. The word "units" has nothing to do with milligrams; it is a volume marking that exists because insulin happens to come at 100 units per ml.

TrialTracker_MD said:

Do it in two steps and it stops being confusing.

TrialTracker_MD has the substance of this right. The condition it depends on is worth stating. The arithmetic is right and one caveat matters: a U-40 syringe changes the markings, not the volumes. If someone hands you U-40 and you read it as U-100 you will be 2.5 times out, and that error has a direction — it is always an overdose.

newstart_MO said:

Two of us with identical vials and identical diluent arrived at different unit counts, which means one of us has a conceptual error rather than a…

Same position here, arrived at the long way round. Concentration choice is a precision decision, not a preference. Reconstitute high and every dose is a tiny volume where one unit of syringe error is a large fraction of the dose. Reconstitute low and you get more graduations per dose, so the same hand tremor costs proportionally less. Against that, more diluent means more benzyl alcohol and a shorter comfortable in-use window.

Clinical perspective, offered as context rather than as advice.

Ongoing cost tracking for dosing arithmetic — transparency for the community:

Monthly medication cost: $158
Supplies (syringes, BAC water, alcohol swabs): ~$11/month
Janoshik testing: ~$13/month (amortized quarterly)
Lab work: ~$48/month (amortized quarterly)
Total: ~$198/month

Compare to brand Wegovy at $1248/month without insurance. Compounded is roughly 88% cheaper for what I have found to be clinically equivalent medication.