Shortages, supply and running out

Demand for these medicines outran manufacturing capacity almost as soon as they became widely known, and supply has been uneven ever since. Shortages have moved between products and between countries rather than affecting everything at once, which is inconvenient in a specific way: the product you are on can become unavailable while the one next to it on the shelf is fine.

The practical consequences are entirely manageable, but only if they are anticipated. This page is about anticipating them.

Know your run-out date

The single most useful habit is also the least interesting. Count the doses you have left, work out the date they run out, and order before the last one rather than on it.

Most missed doses that have nothing to do with forgetfulness happen because someone discovered the problem at the point of collection. A two-week buffer turns "the pharmacy has none" from a crisis into an errand.

Ask the question before you need the answer

At your next appointment, ask: if this becomes unavailable, what would we do?

The answer is worth having in advance because it is not always obvious. It might be a different brand of the same molecule, a different molecule altogether, a different strength combination that achieves a similar dose, or a period of holding at a lower dose. Some of those need a new prescription; some need a fresh authorisation; several take longer to arrange than the gap allows.

A prescriber asked this in advance can note an alternative. A prescriber contacted on the day your pen runs out is working under a deadline.

If your pharmacy cannot fill it

1. Ask them to check other branches or wholesalers. Availability differs between suppliers and often between branches of the same chain.
2. Ask whether a different strength combination works. Sometimes the specific pen is out and another arrangement reaches the same dose — a prescribing decision, but one your pharmacist can flag.
3. Contact your prescriber early, not after several days of searching. They may be aware of what is actually available locally.
4. Ask about the alternative you agreed in advance. This is where that conversation pays for itself.

What not to do

Two further things to avoid. Do not stretch a supply by taking less than prescribed without telling anyone — it changes your treatment silently and your prescriber will be working from wrong information. And do not use someone else's prescription; dose, product and suitability are individual.

If you do end up with a gap

A single missed dose usually needs no adjustment — take the next one on your usual day at the same strength. The rules per product are here.

Several consecutive missed doses is different. Blood levels fall substantially and gastrointestinal tolerance goes with them, so resuming at your previous dose after a long gap frequently reproduces a first escalation at full strength. Ask before restarting: prescribers commonly step back a rung or two and rebuild, which costs a few weeks and avoids a fortnight of being unable to keep food down.

Switching products because of supply

Sometimes the answer is a different medicine, and that is a legitimate solution rather than a compromise. Two points matter.

Doses are not interchangeable between molecules. There is no conversion factor between semaglutide and tirzepatide, or between either and liraglutide, and a switch normally means starting near the bottom of the new ladder even if you were near the top of the old one.

Where the two products share a molecule — the same substance under a different brand — the switch is pharmacologically simple, but the licence and the dose ceiling may differ, so it is still a prescribing decision. Our comparisons set out what changes in each case.

Building a treatment that survives a shortage

• Keep a buffer. Ordering a week early, every time, accumulates into resilience without stockpiling.
• Know the alternative before you need it.
• Keep the relationship with one pharmacy. A pharmacist who knows you is considerably more useful than a counter you have never used.
• Do not build a plan that depends on one specific brand being available every month for years. That plan is more fragile than it looks.

Shortages are frustrating and largely outside your control. The part inside your control is whether one turns into a gap in treatment — and that part is decided by what you did three weeks earlier.

Keeping a buffer without stockpiling

There is a difference between resilience and hoarding, and the line is practical rather than moral. Ordering a week early, every time, gradually builds a few weeks of margin without anyone else going without — and that margin is what turns a supply interruption into an inconvenience.

Stockpiling months of medicine is a different matter. It contributes to the shortage, it means holding more product than your fridge and in-use windows comfortably allow, and it tends to produce pens that expire unused. A buffer of two or three doses does almost all of the work.

Related

• Compounded and unofficial GLP-1s — Cheaper, easier to obtain, and not the same product. What compounding actually is, where the real risks sit, and what regulators have found.

Which medicine you are on

Everything above applies across the class, because it comes from a shared mechanism. The numbers that differ — dose ladders, missed-dose windows, in-use storage periods, half-lives — differ by product, sometimes substantially. Each medicine has its own reference here:

Ozempic · Wegovy · Mounjaro · Zepbound · Rybelsus · Saxenda · Victoza · Trulicity · all medicines