The problem

You've seen it on Reddit, Mumsnet, and private clinic WhatsApp groups:

"I'm on the Wegovy pill at 25mg and want to switch to the injection. The nurse said start at 0.5mg. Isn't that a huge drop?"

Or:

"The oral semaglutide is 14mg but the injection is only 2.4mg. Aren't I getting way more medicine with the pill?"

No. The mg numbers on the pill and the injection are not measuring the same thing.

The confusion comes from a single fact: the dose units mean different things depending on how you take the drug.

The core issue: bioavailability

Bioavailability is how much of the drug actually gets into your bloodstream.

The injection

• You inject into the fat just under the skin
• Almost all of it reaches your bloodstream
• So a 0.5 mg injection is close to 0.5 mg getting to work in your body

The oral pill

• You swallow it
• It has to survive stomach acid and get absorbed through the gut lining
• Only around 1% of oral semaglutide makes it into your bloodstream (Rybelsus SmPC)

That is why the tablet is measured in far bigger mg numbers than the injection. Rybelsus goes up to 14 mg and the Wegovy weight-loss pill is 25 mg, while the injections top out at 2.4 mg. Bigger number, but most of it never reaches your blood. The mg on the box is what you swallow, not what you absorb.

Why there's no conversion table

Here is where a lot of online advice goes wrong. People take that "1% bioavailability" fact and try to build an mg-to-mg conversion out of it, as if you could multiply your injection dose by some number and land on the matching pill dose. You can't, and you shouldn't.

No regulator publishes an mg-to-mg conversion between the oral and injectable forms. The FDA and MHRA labels don't give one, because there isn't a clean one to give. Bioavailability is an average, it varies from person to person, and the way a drug behaves in your body doesn't reduce to a tidy multiplier.

Dosing is clinical, not arithmetic. When you switch formats you don't carry your old dose across on a calculator. You start on the new medicine's own schedule and titrate up, guided by how you respond and tolerate it. If you previously saw a neat "5 to 6x" or "3.5x stronger" rule of thumb here, we've removed it, because it was inventing numbers that don't hold up.

Does the pill work as well?

This is the question underneath all the mg worry: if the injection delivers more to my blood, is the pill just weaker? At the top dose, no.

In the OASIS 4 trial, oral semaglutide 25 mg produced about 14% weight loss at 64 weeks, which the researchers found comparable to the 2.4 mg weekly injection (OASIS 4, ACC). So even though the pill needs a much larger mg number and only around 1% is absorbed, the dose was set so the end result matches the injection. That is exactly why you can't read the raw mg figures as a strength comparison.

Worth separating from this: the lower-dose Rybelsus tablets (3, 7, 14 mg) are licensed for type 2 diabetes and do produce less weight loss than the high-dose pill. That is a different product at a different dose, not proof that "pills are weaker."

Why the confusion happens

Reason 1: same brand name, different numbers

Novo Nordisk uses the Wegovy name for both the injection and the pill, but the doses are on completely different scales. It looks like they should line up. They don't.

Reason 2: people assume "mg is mg"

For most medicines, 10 mg means 10 mg of active ingredient reaching you. But when the route of administration changes, how much actually gets absorbed changes with it.

Reason 3: dose changes don't always get explained

Some clinics just say "start at 0.5 mg" without explaining why the number dropped so far from a 25 mg pill. That silence is where the panic starts.

The absorption enhancer

Here's the detail that makes an oral GLP-1 possible at all: oral semaglutide tablets contain an absorption enhancer called sodium N-(8-[2-hydroxybenzoyl]amino)caprylate, usually shortened to SNAC.

What it does is create a small, local, temporary window in the stomach lining that lets semaglutide cross into the blood before the tablet moves on. Without something like SNAC, a peptide this size would be absorbed almost not at all, and an oral version simply wouldn't work. Even with it, bioavailability sits at roughly 1%, which is why the tablet still needs a large mg dose and strict timing on an empty stomach (Rybelsus SmPC).

What you need to know

1. Don't compare the mg numbers directly. A 25 mg pill is not "ten times" a 2.4 mg injection.
2. There is no official conversion. If you switch formats, you start the new medicine on its own schedule and titrate, you don't convert your old dose.
3. At the top dose the pill works about as well as the injection, per OASIS 4. The weaker option is low-dose Rybelsus, which is a different product for diabetes.
4. Your prescriber decides the dose. If they change your prescription without explaining the new number, ask them to talk you through it.

The FAQ we hear

Q: "I'm on a 1.0mg injection and want to try the oral version. What dose do I ask for?"

A: You don't pick it off a conversion chart. You ask your prescriber, who will start you on the tablet's own titration schedule and step you up from there.

Q: "The pill is 25mg and the injection is 2.4mg. Am I getting ten times the medicine?"

A: No. Only about 1% of the tablet is absorbed. The big mg number offsets the low absorption, which is why the 25 mg pill ends up roughly as effective as the 2.4 mg injection.

Q: "Does this mean the pill is less effective than the injection?"

A: Not at the top dose. OASIS 4 found oral semaglutide 25 mg comparable to the 2.4 mg injection. The lower-dose Rybelsus tablets do less, but that's a different dose for a different use.

A note on what's next

The oral GLP-1 field is moving fast. Eli Lilly's oral drug, orforglipron, is a once-daily pill sold as Foundayo, and it was already approved by the FDA in April 2026 (Drugs.com). It is not yet available in the UK. We cover it in our Foundayo explainer. The Wegovy pill, meanwhile, was approved by the MHRA in June 2026 and is available privately in the UK (GOV.UK).

For now: if you're switching between formats, ask your prescriber how the dose changes. Don't do the maths yourself. The mg numbers are different, but the medicine is the same.