Free calculator

How long will my vial or pen last?

Doses left, the date you run out and when to reorder, from the supply and schedule you enter.

Enter what you have, the dose and schedule you take, and any dose changes your prescriber has set, and this works out how many doses your supply covers, the date it runs out and when to reorder.

It walks the schedule forward one shot at a time, at the dose each shot will be, the same way Tirzing's own supply runway does, so a planned change is counted instead of assuming today's dose forever. Single-dose pens are counted whole.

What's your supply?
mg
As printed on the vial's label.
mg
From a vial you've started.
mg
Only extra you have actually drawn from your vials before. Leave it at 0 if you're not sure.

mg
As your prescriber set it.
days
However long your pharmacy usually takes, plus a margin.

An estimate from the numbers you entered. Not medical advice or information about your medication. Follow your prescriber. It assumes every dose is taken on the schedule you entered and is only as right as those numbers. A vial can give slightly less than the sums say, because some liquid stays in the syringe with each draw. Your pharmacy knows how long an order really takes. Tirzing doesn't sell, recommend or endorse any medication.

Questions people ask

How does it work out how long a vial lasts?

It takes each shot on the schedule you enter, at the dose you enter for that date, out of the supply you enter, until there isn't enough left for the next one. A 10 mg vial and a 0.5 mg dose, for example, cover 20 shots.

Why can a vial run out sooner than dividing by today's dose?

Because a planned dose change uses the supply faster. Tick "My dose changes on a schedule", enter the changes as your prescriber set them, and every shot is counted at the dose it will be.

How does it count single-dose pens?

Each shot uses a whole pen, so a pen is never split across two shots. If a dose is more than one pen holds, that shot uses more than one pen.

How do I enter a KwikPen?

Choose KwikPen and enter what its label says: the amount in each dose and how many doses the pen holds, then how many pens you have.

How does the reorder-by date work?

It is a set number of days before your last covered dose. Pick the lead time that matches how long your pharmacy, delivery and any prescription renewal usually take.

Try the other free tools

A run-out date that keeps itself up to date

In Tirzing, every shot you log draws down the vial or pen it came from, so your run-out date and reorder warning move on their own. It reads your dose plan, counts overfill you've actually drawn, and splits a vial you share with someone else.