Longevity

Microdosing weight-loss medication: what the evidence says

Medically reviewed by Dr Martin Galy, Co-Founder & Director of Wellness & Longevity · Published 14 November 2026 · Last reviewed 14 November 2026

Quick answer: "Microdosing" means taking a prescription weight-loss medicine at doses lower than those tested in clinical trials. There are no human studies of it yet, but it is attracting a lot of attention because of positive feedback from patients, and early laboratory and animal research is exploring possible benefits. Until that evidence exists, any change of dose should be planned with your doctor.

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What are weight-loss injections, and how do they work?

Today's prescription weight-loss injections copy a natural gut hormone called GLP-1, which the body releases after eating. They work in two main ways: they slow how quickly food leaves the stomach, so people feel full for longer, and they act on the brain to turn down hunger signals.

The first medicine in this family was approved for type 2 diabetes in 2005 in the US and 2006 in Europe, so they have been in use for about 20 years [9]. The first GLP1 license for weight management was granted in late 2014 in the US and 2015 in Europe [10].

In the UK, they are licensed for adults with a BMI of 30 or more, or 27 or more with at least one weight-related health condition, alongside a reduced-calorie diet and more physical activity [1]. NICE recommends use within specialist weight management services, for a limited time [1].

In Dr Galy’s experience, some people who use lower doses do so with the intention of reducing food noise and quietening inflammation-related complaints, such as allergies and sensitivities, rather than to lose a lot of weight. While there is currently little or no data to support this, it is attracting growing interest, and early laboratory and animal research is exploring possible benefits. Until that evidence exists, any change of dose should be planned with your doctor.

What does "microdosing" mean?

"Microdosing" is a term patients created, not a medical one. It usually means injecting a fraction of a standard dose, often to reduce side effects, make a pen last longer or keep some benefit at a lower dose. These doses have not been tested in clinical trials. A 2026 narrative review found limited direct evidence on microdosing and noted that it is off-label, and that splitting doses from existing pens raises its own sterility and safety questions [2].

Dr Galy's view is that lower doses can have a place in a doctor-supervised plan, particularly when someone is coming down gradually from treatment, but that this is clinical experience, not proven by research.

Does a lower dose still reduce inflammation?

Some people report that a lower dose seems to ease other symptoms, but there is no research on microdosing for this. At standard doses, there is human evidence: in three large trials, one weekly medicine in this family lowered C-reactive protein (CRP), a blood marker of inflammation, by around 40% to 50% compared with placebo over 68 weeks [3]. Those reductions happened alongside weight loss, so it is not clear how much is a separate effect. Whether smaller doses do the same is unknown.

Is there any evidence that GLP-1 medicines have anti-inflammatory effects?

Yes, some, mostly at standard doses. Trials show these medicines lower CRP, a blood marker of inflammation [3], and researchers are now asking whether that matters in other conditions, including after cancer. Some people who have had cancer already take these medicines, usually because they also have diabetes or obesity, which is what the medicines are licensed for. Researchers are now looking closely at how they do. A 2026 study of women with breast cancer found that those with obesity who took these medicines had a lower risk of the cancer coming back, and of dying, than those who didn't [11]. One idea is that lower inflammation plays a part.

This is promising, but it is not proof. These studies looked back at patients' records; they did not give the medicine to one group and compare it with another, so they can't show the medicine caused the difference. They also studied people on standard doses, not low doses. A 2026 review concluded that more research is needed on both the benefits and the safety of these medicines after cancer [12]. They are not a cancer treatment, and they are not suitable for everyone: people who have had a type of thyroid cancer called medullary thyroid cancer should not take them [13].

If you have had cancer, speak to your oncologist before starting, stopping or changing any of these medicines.

What side effects do weight-loss injections cause?

The most common side effects are nausea, constipation, diarrhoea and tiredness, usually worst when the dose goes up. Hair shedding can happen, especially with any fast weight loss. Serious side effects are rare but real. In January 2026 the UK medicines regulator, the MHRA, strengthened its warnings about acute pancreatitis, which in very rare cases can be severe or fatal, and advised urgent medical help for severe, persistent stomach pain that may spread to the back [4]. There is also an association between the use of GLP-1 medicines and sudden blindness, seen in people with type 2 diabetes. We explain what that does and doesn't mean below [5, 14].

Does GLP-1 increase the risk of sudden blindness? What the November 2026 FDA warning actually says

On 9 November 2026, the US Food and Drug Administration (FDA) issued a warning about an increased risk of a condition called NAION in people using GLP-1 medicines. NAION stands for non-arteritic anterior ischaemic optic neuropathy, which is quite a mouthful, so we will simply call it sudden blindness rather than use the technical term. You can think of it as a stroke of the optic nerve: blood flow to the front of the nerve drops, and the sight in one eye can go suddenly and painlessly, often for good. The warning now covers every medicine in this family, and much of the evidence behind it comes from studies of people with type 2 diabetes [14].

So what does that actually mean? Essentially, these studies show an association, not a causation: people with diabetes taking GLP-1 medicines developed sudden blindness more often than similar people who weren't taking them. What they don't show is that the medicine itself is the actual cause. That difference, between association and causation, really matters.

Here is a simple example. The people most likely to be prescribed these medicines often already have insulin resistance, type 2 diabetes or high blood pressure, and each of those carries its own increased risk of sudden blindness. Add a new medicine into that group and the risk may look higher, but we don't yet have enough evidence to say the medicine is the cause, rather than the conditions people already had. The extra risk is also very small: the UK and European regulators estimate around one extra case for every 10,000 people treated for a year [5].

There are two gaps in the current evidence. First, we don't know the specific rate of sudden blindness in the general population without diabetes. Second, we don't know whether that rate goes up in people without diabetes who use GLP-1 medicines.

The only thing we do know is that people with type 2 diabetes have an increased risk when they are using GLP-1 medicines [5, 14]. What we don't know, because of these gaps in the studies, is 1) whether the medicine is the cause or whether it is an association, and 2) whether the same increased risk applies to people without diabetes.

What to do is simple. If your sight changes suddenly, especially in one eye, contact your doctor straight away.

This is why doctors check blood tests before and during treatment, start low and increase slowly. Taking more or less than prescribed, or buying medicine outside a prescription, removes that safety net.

What happens when you stop weight-loss injections?

Most people regain weight after stopping. In one trial extension, people who stopped after 68 weeks regained about two-thirds of the weight they had lost within a year, and improvements in blood pressure and blood sugar moved back towards where they started [6]. A 2026 review of 37 studies found people regained an average of 0.4 kg a month after stopping, with weight projected to return to its starting point in about 1.7 years [7].

Dr Galy compares stopping suddenly to stopping blood-pressure medicine once blood pressure is controlled. In his practice, the dose is reduced gradually over time while people keep up their eating and exercise habits. Muscle, fat and visceral fat are measured along the way with a body composition scan (DEXA). You can read more in our article on life after the prescription.

Can diet raise your own GLP-1?

Protein and fibre-rich meals with regular exercise may improve the body's own production of appetite hormones, including GLP-1. Medicines have a much stronger effect. What matters more during treatment is eating enough, because with a reduced appetite, it is easy to fall short on protein, fibre and fluid intake [8]. Protein and strength training help protect muscle, which we cover in our article on muscle loss during weight loss.

Results vary from person to person, and a doctor will discuss the benefits and risks of any treatment with you.

The 23MD view

As of now, there is very little evidence for GLP-1 microdosing, so I wouldn't present it as a proven way to lose weight. However, coming off treatment slowly and safely, rather than stopping overnight, in my experience helps patients regain control over their food noise and makes it less likely that the weight comes back. Whatever the dose, the essentials don't change: blood tests before and during treatment, enough protein, strength training, and measuring muscle and visceral fat, not just weight. That is the approach we take in our metabolic assessment.

Who this is for, and who it isn't for

This may be useful if:

you have heard about microdosing and want to know what the evidence says;
you are taking a prescribed weight-loss medicine and are thinking about the next step.

This isn't for you if:

you are thinking of buying weight-loss medicine without a prescription. Please speak to a doctor first;
you have severe, persistent stomach pain or a sudden change in your vision while taking one of these medicines. Seek urgent medical help.

Frequently asked questions

What are weight-loss injections?

They are a class of medicines called GLP-1 medicines, first developed to treat type 2 diabetes about 20 years ago [9]. They have been licensed for weight management in the UK since 2015 [10].

How do weight-loss injections work?

They work in two main ways: they slow how quickly food moves through the gut, so you stay full for longer between meals, and they change the way the brain receives and responds to hunger messages.

What side effects do you see and how are they managed?

The complaints I hear most are tiredness, constipation and nausea. Some people notice hair shedding, which can be helped with diet changes and supplements. More serious risks include pancreatitis. If you get severe or persistent stomach pain whilst taking these medications, you should seek urgent medical advice. There is also an association between GLP-1 use and sudden blindness (NAION), with an increased association in people with type 2 diabetes. It is very rare, and an association is not proof that the medicine is the cause. If you notice any sudden change in your sight, contact your doctor straight away; if sudden blindness is confirmed, the medicine is stopped [5, 14]. In my experience, side effects are limited when treatment is prescribed cautiously: diet and calorie advice from the start, no high doses unless necessary, and blood tests before and during treatment to check the organs these medicines can affect. If blood tests show the pancreas is under strain, the medicine is stopped [4].

Does the use of GLP-1 medicines cause blindness?

We don't know that it does. The FDA warning of 9 November 2026 reflects studies that show an association between GLP-1 medicines and a rare condition called NAION (non-arteritic anterior ischaemic optic neuropathy), which I call sudden blindness rather than the technical term. Most of those studies were in people with type 2 diabetes [14]. What the warning doesn't do is prove that GLP-1 medicines cause the increased risk.

Many of the people taking these medicines already have diabetes, insulin resistance or high blood pressure, and each of those raises the risk of sudden blindness on its own, so we can't yet separate the effect of the medicine from the conditions people already had. The extra risk is very small, around one extra case for every 10,000 people treated for a year [5].

If your sight changes suddenly, especially in one eye, contact your doctor straight away. If sudden blindness is confirmed, the medicine is stopped [5, 14].

What does "microdosing" mean, and does the evidence support it?

There is very little evidence for it yet. "Microdosing" is a term patients created for doses that have not been recommended or researched in clinical trials [2]. In my experience, lower doses can help, especially when coming down from treatment, but that is clinical experience, not proven research. At standard doses, trials show a fall in CRP, a marker of inflammation [3]; whether smaller doses do the same is not known.

What happens when people stop weight-loss injections?

I don't recommend stopping suddenly after losing weight successfully. It would be like stopping blood-pressure medicine once blood pressure is under control. Stopping before someone is ready usually brings the weight back and can worsen blood-sugar control [6, 7]. I prefer to bring the dose down gradually over months, just as it was built up over months, while keeping healthy eating and exercise habits and measuring muscle, fat and visceral fat.

Can diet raise the body's own GLP-1, and what should you eat alongside treatment?

A diet high in protein and fibre, with regular exercise, may support the body's own GLP-1, but it is unlikely to work as well as the medicine. Alongside treatment, I advise keeping protein intake up, weight training to protect muscle, and checking hormone levels during and after treatment [8].

Talk to a 23MD doctor

If you are considering weight-loss medicine, or want to come off it safely, speak to our team. Your consultation is with a doctor, who will look at your health as a whole and talk you through the options honestly.

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