Does Wegovy have B12 in it? No, Wegovy does not contain vitamin B12. This prescription weight-loss medicine contains only semaglutide, a GLP-1 receptor agonist, along with pharmaceutical excipients. Whilst Wegovy itself has no B12, concerns about vitamin B12 status during treatment arise because the medication significantly reduces appetite and food intake. This may inadvertently lower consumption of B12-rich foods such as meat, fish, dairy, and eggs. Understanding the relationship between Wegovy and B12 is important for maintaining nutritional health during weight management therapy.

What Is Wegovy and How Does It Work?

Wegovy does not contain vitamin B12. It is a prescription-only medicine containing semaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist licensed in the UK for weight management in adults with obesity or overweight with weight-related health conditions. Semaglutide is the sole active pharmaceutical ingredient in Wegovy, and the formulation includes only pharmaceutical excipients necessary for stability and delivery—no vitamins or nutritional supplements are present.

Wegovy works by mimicking the action of GLP-1, a naturally occurring hormone released by the intestine after eating. By binding to GLP-1 receptors in the brain, particularly in areas that regulate appetite, semaglutide reduces hunger and increases feelings of fullness. This mechanism helps patients consume fewer calories without the intense hunger often associated with calorie restriction. Additionally, Wegovy slows gastric emptying, meaning food remains in the stomach longer, which contributes to prolonged satiety between meals.

The medication is administered once weekly via subcutaneous injection, typically in the abdomen, thigh, or upper arm. Treatment begins at a low dose (0.25 mg weekly) and is gradually increased over 16–20 weeks to the maintenance dose of 2.4 mg weekly. This titration schedule minimises gastrointestinal side effects, which are the most commonly reported adverse reactions. According to NICE technology appraisal guidance (TA875), Wegovy should be prescribed as part of a specialist weight management service, with specific eligibility criteria including BMI thresholds and weight-related conditions. Treatment should be stopped if less than 5% of body weight is lost after 6 months at the maintenance dose, and the maximum treatment duration is 2 years. Wegovy should be used alongside dietary modification, increased physical activity, and behavioural support.

If you experience any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in the package leaflet. You can also report side effects directly via the Yellow Card Scheme at yellowcard.mhra.gov.uk.

Why B12 Deficiency Matters When Taking Wegovy

Whilst Wegovy itself contains no vitamin B12, concerns about B12 status during GLP-1 receptor agonist therapy arise primarily from the medication's effects on eating patterns. Vitamin B12 (cobalamin) is essential for red blood cell formation, neurological function, and DNA synthesis. Deficiency can lead to megaloblastic anaemia, peripheral neuropathy, cognitive impairment, and fatigue—symptoms that may overlap with or be mistaken for side effects of weight loss medications.

The primary concern relates to reduced dietary intake. Wegovy significantly decreases appetite and food consumption, which is its intended therapeutic effect. However, if patients consume substantially less food—particularly animal products such as meat, fish, dairy, and eggs, which are the main dietary sources of B12—they may inadvertently reduce their B12 intake below recommended levels. The NHS recommends adults obtain approximately 1.5 micrograms of vitamin B12 daily, and prolonged inadequate intake can deplete body stores over months to years.

Additionally, gastrointestinal side effects associated with Wegovy—including nausea, vomiting, diarrhoea, and constipation—may affect overall food intake or further limit dietary variety. While there is no established causal link between semaglutide and direct impairment of B12 absorption (which requires intrinsic factor produced by gastric parietal cells), persistent gastrointestinal symptoms could theoretically impact overall nutritional status. Patients who experience prolonged nausea or vomiting may struggle to maintain adequate intake of B12-rich foods, compounding the risk of deficiency. Those with pre-existing risk factors—such as pernicious anaemia, previous gastric or bariatric surgery (who often require lifelong B12 supplementation), long-term metformin use, or strict vegetarian/vegan diets—warrant particular attention regarding B12 status during Wegovy treatment.

Managing B12 Levels During Wegovy Treatment

Proactive monitoring and dietary planning are essential to maintain adequate B12 levels during Wegovy therapy. Before starting treatment, healthcare professionals should assess baseline nutritional status, including any pre-existing deficiencies or risk factors for B12 deficiency. Patients with known B12 deficiency should have this addressed prior to or concurrent with initiating Wegovy, as weight loss therapy may exacerbate existing nutritional inadequacies.

Dietary strategies form the cornerstone of B12 maintenance. Even with reduced appetite, patients should prioritise nutrient-dense foods at mealtimes. Excellent sources of vitamin B12 include:

• Meat and poultry: beef, lamb, chicken, and particularly organ meats like liver

• Fish and seafood: salmon, trout, tuna, sardines, and shellfish

• Dairy products: milk, cheese, and yoghurt

• Eggs: particularly the yolk

• Fortified foods: certain breakfast cereals, plant-based milk alternatives, and nutritional yeast

For patients following vegetarian or vegan diets, fortified foods and supplementation become particularly important, as plant foods do not naturally contain bioavailable B12. For prevention, supplements providing 10-50 micrograms daily or 2000 micrograms weekly are typically recommended for those on plant-based diets. These are available over-the-counter and are generally well-tolerated.

Regular monitoring may be appropriate for high-risk patients. Whilst routine B12 testing is not standard for all Wegovy users, those with symptoms suggestive of deficiency—such as unusual fatigue, pins and needles, memory problems, or glossitis—should have serum B12 levels checked. UK laboratories typically consider levels below 148 pmol/L (approximately 200 ng/L) as deficient, though reference ranges vary between laboratories and borderline results may require confirmatory testing with methylmalonic acid or holotranscobalamin. If deficiency is confirmed, treatment options include oral B12 supplements (typically 50–150 micrograms daily for dietary deficiency) or, in cases of malabsorption, intramuscular hydroxocobalamin injections (1 mg three times weekly for two weeks, then 1 mg every 2-3 months for maintenance) according to British National Formulary guidance.

When to Speak to Your GP About B12 and Wegovy

Patients should contact their GP or prescribing specialist if they develop symptoms potentially related to B12 deficiency during Wegovy treatment. Key warning signs include:

• Neurological symptoms: persistent tingling, numbness, or 'pins and needles' in hands or feet; balance problems; memory difficulties or confusion

• Haematological signs: unusual tiredness or weakness that doesn't improve with rest; pale or jaundiced skin; shortness of breath with minimal exertion

• Oral changes: a sore, red tongue (glossitis); mouth ulcers that don't heal

• Mood changes: depression, irritability, or cognitive difficulties beyond what might be expected

These symptoms may have many causes and require clinical assessment regardless of whether they're related to B12 deficiency. For severe or rapidly progressive neurological symptoms, seek urgent medical advice via NHS 111 or urgent care services. Early detection and treatment of B12 deficiency is important because neurological damage, if prolonged, may become irreversible even after B12 levels are corrected.

Patients should also discuss B12 with their healthcare provider if they have pre-existing risk factors, including pernicious anaemia, previous gastric or bariatric surgery, Crohn's disease or coeliac disease, long-term use of metformin or proton pump inhibitors, or adherence to strict plant-based diets. In these cases, baseline B12 testing before starting Wegovy and periodic monitoring during treatment may be advisable.

Follow-up appointments for Wegovy will be arranged by your specialist weight management service, providing opportunities to discuss nutritional concerns. Remember that treatment should be stopped if less than 5% of body weight is lost after 6 months at the maintenance dose, and the maximum treatment duration is 2 years. Patients should be prepared to describe their dietary intake, any persistent gastrointestinal symptoms, and any new or worsening symptoms. If significant dietary restriction or persistent nausea limits food intake, referral to a registered dietitian can provide tailored nutritional guidance to optimise micronutrient intake whilst achieving weight loss goals. Successful weight management with Wegovy depends not only on the medication itself but on maintaining overall health and nutritional adequacy throughout the treatment journey.

Frequently Asked Questions