GLP-1 and Your Other Medications

Written by Dr Jatin Joshi, co-founder and Chief Medical and Scientific Officer of Personally, and a researcher at the University of Oxford's Centre for Evidence-Based Medicine. I have a financial stake in this company, and you should weigh what follows with that in mind.

You are on a GLP-1, you take other things as well, whether that is prescription medicines or supplements, and you have started to wonder whether the GLP-1 changes how any of it works. It is a sensible question to be asking, and the most useful thing I can do is be clear about which parts of the answer belong to whom, because some of it is firmly your prescriber's and pharmacist's territory, and only a narrower part of it is mine.

So let me split the job honestly.

Whether one medicine changes how another one works, whether two of your prescriptions should be spaced apart, whether a dose needs adjusting, all of that is a clinical decision that belongs with the people who can see your full list and your full history. It is not something to work out from an article, and I am not going to try to answer it for you here, because doing so responsibly would need to know everything you take and why, which I cannot.

There are a couple of specific reasons this matters more on a GLP-1 than people expect. These medicines slow how quickly your stomach empties, and for some oral medicines that can affect how or when they are absorbed. If you take other tablets, it is worth asking your pharmacist directly whether the timing of any of them is affected. And if your GLP-1 sits alongside other glucose-lowering medicines, the combination can change your risk of your blood sugar dropping too low, which again is a conversation for your prescriber. None of this is a reason to stop or alter anything on your own. It is a reason to have one clear conversation with your pharmacist, who is very good at exactly this and often has more time for it than your doctor does.

If you take anything you would call a supplement as well, that belongs in the same conversation. Adding supplements on top of prescription medicines is precisely the kind of thing worth running past a pharmacist, rather than assuming that because something is sold without a prescription it cannot interact with one.

Here is the part that is genuinely about nutrition, and it follows from the simplest fact about how these medicines work: they reduce your appetite, so you eat less. That is the point of them. But eating less has a consequence that is easy to miss while the number on the scale is moving in the direction you wanted. When the total amount of food coming in drops, the amount of protein and key nutrients coming in usually drops with it, and it can drop below what your body actually needs even as your weight falls.

So the nutritional question changes shape. It stops being about eating less and becomes about making the smaller amount you do eat count for more. Protein matters more per meal, not less, precisely because there are fewer meals and smaller ones. The same is true of the vitamins and minerals that are easy to fall short on when portions shrink, and of fibre and simple hydration, which often slip when appetite does.

Let me be careful, because this is exactly the area where supplement companies overreach. Nutrition cannot make your GLP-1 work better, it cannot replace it, and it is not a treatment for the side effects that belong to the medicine. If you are getting nausea or anything else that troubles you, that is a conversation with your prescriber, not something to manage with a product.

What nutrition can honestly do is help you fill the gaps that open up when your intake falls. That is a real and worthwhile job, and it is a different claim entirely from the ones above.

Muscle is worth a specific mention, because it worries people and because it is misused in marketing. When you lose weight quickly, by any method, some of what you lose is muscle alongside fat. The two things with the best evidence for holding on to muscle while that happens are getting enough protein and doing some form of resistance exercise, and both of those belong to what you eat and how you move, not to a tub. Nutrition's honest role is to help you actually reach adequate protein and nutrient intake when you are eating much less than before, which is genuinely harder than it sounds on a shrunken appetite. Anyone promising you that a supplement prevents the muscle loss is selling you past the evidence.

This is the point of the whole piece, really. On a GLP-1, your appetite drops and so can your intake of protein and key nutrients, and the nutritional gaps that open up as your body changes are a real thing worth formulating around, alongside your medication and your clinician's care. That is the specific job we are built for.

The one thing that makes it work is the thing most of the industry skips: we ask what you take. When you tell us your medications, we screen them for relevant interaction and nutrient considerations before we formulate, rather than handing you the same blend as everyone else and hoping. That is not a comprehensive medication-safety service, and it does not replace the pharmacist conversation above, it is a narrower and honest thing: your supplement should at least know what else you are taking, and most do not.

If you want to see what that looks like for your particular situation, the quiz is where it starts. It will ask what you take, which is rather the point, and it is a way to understand where nutrition fits around your medication, not a checkout.

The order that keeps you safe is simple. Take the drug questions to your prescriber and pharmacist. Keep your protein up and move against some resistance. And let nutrition do the specific job of filling genuine gaps, once the medical part is in the right hands.