Which vitamins and supplements are worth taking with Wegovy

Why reduced eating on semaglutide creates real nutritional risk

The STEP 1 trial, published in the New England Journal of Medicine, showed participants on semaglutide 2.4 mg losing an average of around 15% of body weight over 68 weeks, largely through a sustained reduction in hunger and food intake. That's a meaningful reduction in the sheer volume of food passing through the body each week. When total food intake drops that far, the micronutrient maths changes, even if the diet is relatively balanced. Someone eating 1,200–1,400 calories a day instead of 2,000 may be getting under two-thirds of their usual vitamin D, B12, iron, and calcium, depending on food choices.

The foods people tend to skip first on GLP-1 medicines are often the dense, rich ones: red meat, eggs, dairy, oily fish, fortified cereals. These are, inconveniently, the same foods that carry much of the dietary B12, iron, zinc, and omega-3 load. The NHS notes that fatigue, bone health, and immune function are all linked to adequate intake of these nutrients, and that deficiencies can develop gradually and silently.

None of this means supplementation is automatic for every person on Wegovy. A quick habit worth building: once a month, check whether you have eaten a source of protein, an oily fish or fortified food, and a dairy or calcium-rich food on most days that week. If the honest answer is rarely, it's worth raising with your prescriber at the next clinical review. Our dedicated page on which vitamins to take when on Wegovy walks through the key considerations in detail. You can also read more about how Wegovy and vitamins interact in broader terms.

Vitamin D and bone health: the gap most often missed

Vitamin D sits at the top of most clinician priority lists for people on weight-loss medicines, for two reasons. First, dietary sources are limited even on a full diet, oily fish, egg yolks, and fortified foods contribute some, but UK sunlight alone is insufficient for most of the year. Second, rapid weight loss can accelerate bone density loss, particularly if protein and calcium intake are also low. The NHS semaglutide medicines page signposts general health monitoring during treatment, and bone health forms part of that picture.

The UK Government's Scientific Advisory Committee on Nutrition recommends that all adults consider a daily 10 micrograms (400 IU) vitamin D supplement, particularly between October and March. For someone on a GLP-1 medicine with substantially reduced dairy and oily fish intake, a year-round supplement is a sensible discussion to have with a prescriber. Calcium is linked here too: if dairy intake has dropped, the body draws more heavily on bone calcium stores over time. Some clinicians recommend a combined vitamin D and calcium supplement for patients who have largely eliminated dairy.

More detail on the specific relationship between vitamin D and Wegovy is worth reading if bone health is a concern for you.

B12, iron, and the nutrients tied to energy and red blood cells

Vitamin B12 is found almost exclusively in animal products: meat, fish, dairy, eggs. On a calorie-restricted diet where portion sizes have shrunk and red meat in particular often becomes less appealing, B12 intake can quietly fall below the level needed to maintain healthy nerve function and red blood cell production. Symptoms of B12 deficiency, including fatigue, tingling, and brain fog, can develop slowly over months, making it easy to attribute them to the weight-loss process itself rather than a correctable gap.

Iron is a parallel concern, especially for women with higher monthly losses. The foods that carry the most absorbable (haem) iron are the ones most likely to be eaten in smaller quantities on semaglutide: red meat, liver, and fortified cereals. Non-haem iron from plant sources is absorbed less readily, though eating it alongside vitamin C helps. If fatigue or breathlessness develops during treatment, a simple blood test can check ferritin and B12 levels, something to raise with a GP or your prescribing clinician.

For a broader overview of vitamins to take while on Wegovy, including practical supplement formats, the linked page covers the topic in full.

Protein and the supplements that support muscle through a calorie deficit

Strictly speaking, protein is a macronutrient rather than a vitamin, but it belongs in this conversation. Clinical guidance around GLP-1 medicines consistently emphasises adequate protein intake to minimise muscle loss during weight reduction. A rough working target, used in many weight-management programmes and supported by general NICE obesity management guidance, is around 1.2–1.6 g of protein per kilogram of body weight per day. At reduced eating volumes, hitting that from whole foods alone is genuinely difficult for many people.

A high-quality protein supplement (whey, casein, or a plant-based equivalent with a complete amino acid profile) can bridge that gap practically without adding significant fat or refined carbohydrate. It is not a medicine and does not require a prescription, but the choice of supplement and the appropriate target are worth discussing with a prescriber or dietitian who knows your full clinical picture.

The full guide to what vitamins to take on Wegovy covers supplement forms and timing in more detail. If you are considering starting Wegovy or are mid-treatment and want your nutritional plan reviewed alongside your prescription, semaglutide treatment at nume includes same-day clinical review by a GPhC-registered prescriber. For information on what treatment options are available and how the process works, check your eligibility and our prescribers can talk through the full picture with you.