Wegovy (semaglutide 2.4 mg) is a GLP-1 receptor agonist licensed in the UK for chronic weight management in adults with obesity or overweight with weight-related comorbidities. As with any medication that significantly alters appetite and dietary intake, patients and clinicians may wonder: can Wegovy cause iron deficiency? Whilst there is no direct pharmacological mechanism linking Wegovy to iron depletion, the substantial dietary changes and gastrointestinal effects associated with treatment may indirectly affect iron status. Understanding these potential pathways, recognising early signs of deficiency, and implementing appropriate monitoring strategies are essential for safe and effective weight management. This article examines the evidence, explores indirect mechanisms, and provides practical guidance for maintaining optimal iron levels during Wegovy treatment.

Understanding Wegovy and Its Mechanism of Action

Wegovy (semaglutide 2.4 mg) is a glucagon-like peptide-1 (GLP-1) receptor agonist licensed in the UK for chronic weight management in adults with obesity or overweight with weight-related comorbidities. According to NICE Technology Appraisal 875, Wegovy is recommended for use within the NHS for adults with a BMI of at least 35 kg/m² and at least one weight-related comorbidity, or a BMI of at least 30 kg/m² with type 2 diabetes, when provided through specialist weight management services.

Wegovy is administered as a once-weekly subcutaneous injection, with a dose-escalation schedule over 16 weeks to minimise gastrointestinal side effects. It works through several complementary mechanisms to facilitate weight loss.

The primary mechanism of action involves mimicking the naturally occurring hormone GLP-1, which is released from the intestine in response to food intake. Semaglutide binds to GLP-1 receptors in the brain, particularly in areas that regulate appetite and food intake. This leads to reduced hunger, increased feelings of fullness (satiety), and consequently decreased caloric intake. Additionally, Wegovy slows gastric emptying—the rate at which food leaves the stomach—which prolongs the sensation of fullness after meals and helps reduce overall food consumption.

Beyond appetite regulation, semaglutide also improves glycaemic control by enhancing glucose-dependent insulin secretion from pancreatic beta cells and suppressing inappropriate glucagon release. Whilst Wegovy is primarily indicated for weight management rather than diabetes treatment, these metabolic effects contribute to its overall therapeutic profile.

Clinical trials (STEP programme) have demonstrated that Wegovy, when combined with lifestyle interventions including reduced-calorie diet and increased physical activity, can lead to substantial weight loss—with a mean of approximately 15% of initial body weight over 68 weeks. The medication is prescribed as part of a comprehensive weight management programme and requires ongoing monitoring by healthcare professionals. Understanding how Wegovy works is essential context for evaluating its potential effects on nutritional status, including iron levels.

Can Wegovy Directly Cause Iron Deficiency?

There is currently no established direct pharmacological link between Wegovy (semaglutide) and iron deficiency. The drug's mechanism of action—binding to GLP-1 receptors to regulate appetite and glucose metabolism—does not appear to directly interfere with iron absorption, transport, or utilisation at a cellular or molecular level. There is no evidence to date that semaglutide inhibits the enzymes or transporters responsible for iron uptake in the duodenum, nor that it affects haemoglobin synthesis or red blood cell production.

Review of the Summary of Product Characteristics (SmPC) for Wegovy, as approved by the Medicines and Healthcare products Regulatory Agency (MHRA), does not list iron deficiency or anaemia as recognised adverse effects. The most commonly reported side effects are gastrointestinal in nature, including nausea, diarrhoea, vomiting, constipation, and abdominal pain. These occur in a significant proportion of patients, particularly during dose escalation, but they do not constitute a direct mechanism for iron depletion.

However, the absence of a direct pharmacological mechanism does not entirely exclude the possibility of iron deficiency developing during Wegovy treatment. It is important to distinguish between direct causation and indirect associations. Whilst the medication itself does not appear to deplete iron stores or impair iron metabolism, the physiological and behavioural changes that accompany Wegovy use—particularly significant dietary restriction and gastrointestinal symptoms—may create conditions that affect iron status.

Patients and healthcare professionals should be aware that any observed changes in iron levels during Wegovy treatment are more likely attributable to secondary factors rather than the drug's direct action. This distinction is clinically important for appropriate investigation and management of iron deficiency in this patient population.

Any suspected adverse reactions to Wegovy, including unexpected nutritional deficiencies, should be reported through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or the Yellow Card app).

Indirect Pathways: How Wegovy May Affect Iron Status

Whilst Wegovy does not directly cause iron deficiency, several indirect mechanisms may potentially affect iron status during treatment. Understanding these pathways is essential for comprehensive patient care and appropriate monitoring.

Reduced dietary intake represents the most significant indirect pathway. Wegovy's appetite-suppressing effects lead to substantially decreased caloric consumption, which is the intended therapeutic mechanism for weight loss. However, reduced food intake inevitably means reduced intake of dietary iron. Haem iron from meat, poultry, and fish, as well as non-haem iron from plant sources, legumes, and fortified cereals, may all be consumed in lower quantities. Patients following very restrictive diets or those who eliminate entire food groups may be at particular risk.

Gastrointestinal side effects constitute another important consideration. Nausea, vomiting, and diarrhoea—common during Wegovy treatment, especially in the initial months—can potentially affect nutrient absorption. Persistent vomiting may lead to avoidance of iron-rich foods. While chronic diarrhoea could theoretically impair iron absorption in the small intestine, the clinical significance of this effect specifically with Wegovy has not been well established. Additionally, some patients develop food aversions or changes in taste preferences that may further limit dietary variety.

Delayed gastric emptying, whilst contributing to satiety, may theoretically affect the optimal conditions for iron absorption, which primarily occurs in the duodenum. However, this remains a theoretical concern, and the clinical significance of this effect on iron status is unproven and requires further research.

Finally, rapid weight loss itself may be associated with nutritional deficiencies if not accompanied by adequate dietary planning. Patients losing substantial weight quickly may not maintain sufficient intake of micronutrients, including iron, particularly if they are not receiving appropriate nutritional counselling. Women of reproductive age, individuals with pre-existing low iron stores, and those with heavy menstrual bleeding may be especially vulnerable to developing iron deficiency during Wegovy treatment through these indirect mechanisms.

Recognising Signs of Iron Deficiency During Wegovy Treatment

Early recognition of iron deficiency is crucial for patients taking Wegovy, as symptoms may overlap with common side effects of the medication or be attributed to the weight loss process itself. Healthcare professionals and patients should maintain awareness of the characteristic features of iron deficiency.

Common symptoms of iron deficiency include:

• Fatigue and weakness – persistent tiredness that does not improve with rest

• Pallor – pale skin, nail beds, and mucous membranes (inside lower eyelids)

• Shortness of breath – particularly on exertion or during activities previously well-tolerated

• Dizziness or light-headedness – especially when standing quickly

• Cold hands and feet – due to reduced oxygen delivery to extremities

• Headaches – often frontal and persistent

• Rapid or irregular heartbeat (palpitations)

• Brittle nails or koilonychia (spoon-shaped nails) in more advanced cases

• Sore or swollen tongue (glossitis)

• Unusual cravings for non-food items such as ice, paper, or starch (pica)

• Restless legs syndrome – uncomfortable sensations in legs with urge to move them

• Difficulty concentrating or impaired cognitive function

It is important to note that these symptoms may develop gradually and can be subtle in early stages. Patients may dismiss them as normal consequences of dieting or weight loss. Additionally, some symptoms—particularly fatigue and gastrointestinal disturbances—may be difficult to distinguish from Wegovy's known side effects.

Iron deficiency progresses through stages: initial depletion of iron stores (low ferritin), followed by iron-deficient erythropoiesis (reduced serum iron and transferrin saturation), and finally iron deficiency anaemia (low haemoglobin). According to British Society of Haematology guidelines, a ferritin level below 15 µg/L is diagnostic of iron deficiency, while levels below 30 µg/L suggest probable deficiency. In the presence of inflammation, a ferritin below 100 µg/L with transferrin saturation below 20% may indicate iron deficiency. Blood tests may also show microcytosis (small red cells) and low mean cell haemoglobin (MCH) in iron deficiency anaemia.

Patients experiencing any combination of these symptoms during Wegovy treatment should report them to their healthcare provider for appropriate assessment, rather than assuming they are inevitable consequences of weight loss therapy.

Monitoring and Managing Iron Levels on Wegovy

Proactive monitoring and management of iron status is advisable for patients undergoing treatment with Wegovy, particularly those at higher baseline risk of deficiency. Whilst routine iron screening is not mandated for all Wegovy patients, a risk-stratified approach is clinically prudent.

Baseline assessment should ideally include a full blood count (FBC) before initiating Wegovy, particularly for patients with risk factors including:

• Women with heavy menstrual periods (menorrhagia)

• Previous history of iron deficiency or anaemia

• Vegetarian or vegan diets

• Gastrointestinal conditions affecting absorption (coeliac disease, inflammatory bowel disease)

• Previous bariatric surgery

• Frequent blood donors

Monitoring during treatment should be individualised based on clinical presentation and risk factors. For higher-risk patients, repeat FBC and iron studies (serum ferritin, serum iron, transferrin saturation) at 3-6 month intervals may be appropriate. If iron deficiency is suspected, initial tests should include FBC, ferritin and C-reactive protein (CRP) to assess for inflammation.

Dietary optimisation represents the first-line approach to maintaining adequate iron status. Patients should receive counselling from a registered dietitian to ensure their reduced-calorie diet includes:

• Haem iron sources: lean red meat, poultry, fish (more readily absorbed)

• Non-haem iron sources: fortified cereals, beans, lentils, dark leafy greens, dried fruit

• Absorption enhancers: vitamin C-rich foods consumed with iron sources

• Avoidance of inhibitors: limiting tea, coffee, and calcium supplements around iron-rich meals

Iron supplementation may be necessary if dietary measures prove insufficient or if deficiency develops. Oral iron supplements are typically first-line, with UK standard dosing being ferrous sulphate 200 mg, ferrous fumarate 210 mg, or ferrous gluconate 300 mg once daily or on alternate days (alternate-day dosing may improve tolerance). Gastrointestinal side effects may be problematic in patients already experiencing Wegovy-related symptoms. Treatment should continue for approximately 3 months after haemoglobin normalisation to replenish iron stores. Alternative formulations or intravenous iron may be considered in cases of intolerance or malabsorption.

Monitoring response to iron therapy should include checking haemoglobin within 2-4 weeks to confirm improvement (expected rise of at least 10 g/L), with periodic testing until normalisation and ferritin testing to confirm repletion of iron stores.

Investigation of underlying causes is essential, particularly in men and postmenopausal women with confirmed iron deficiency anaemia. British Society of Gastroenterology guidelines recommend that these patients should undergo assessment for gastrointestinal blood loss and testing for coeliac disease. Any supplementation should be prescribed and monitored by a healthcare professional.

When to Seek Medical Advice

Patients taking Wegovy should be aware of specific circumstances that warrant prompt medical review regarding potential iron deficiency or related complications. Clear guidance on when to contact healthcare services supports patient safety and enables timely intervention.

Contact your GP or prescribing clinician if you experience:

• Persistent or worsening fatigue that interferes with daily activities and does not improve with adequate rest

• Significant breathlessness during normal activities or at rest

• Chest pain or palpitations – these require same-day assessment

• Severe or persistent dizziness, particularly if associated with fainting episodes

• Marked pallor noticed by yourself or others

• Unusual food cravings (pica) or restless legs syndrome

• Difficulty concentrating or cognitive changes affecting work or daily function

• Heavy menstrual bleeding or any unexplained bleeding

• Signs of gastrointestinal bleeding – black or tarry stools, persistent change in bowel habit, unintentional weight loss beyond expected with Wegovy, or difficulty swallowing

Seek urgent medical attention (call 999 or attend A&E) if you develop:

• Severe chest pain or pressure

• Sudden severe breathlessness

• Loss of consciousness or near-fainting

• Rapid heart rate with chest discomfort

These symptoms may indicate severe anaemia or other serious conditions requiring immediate assessment.

Important note for men and postmenopausal women: If you are diagnosed with iron deficiency anaemia while taking Wegovy, this will typically require prompt investigation of the gastrointestinal tract to identify the cause. This is because iron deficiency anaemia in these groups may be a sign of gastrointestinal blood loss, including from serious conditions such as colorectal cancer, and may meet criteria for urgent suspected cancer referral pathways.

Routine follow-up with your prescribing clinician is essential during Wegovy treatment. These appointments provide opportunities to discuss any concerns about nutrition, review blood test results, and adjust management plans as needed. Do not discontinue Wegovy without medical advice, even if you suspect iron deficiency—your healthcare provider can address both issues concurrently.

Before starting Wegovy, discuss your individual risk factors for iron deficiency with your healthcare provider. If you have pre-existing anaemia, heavy periods, or dietary restrictions, ensure these are documented and appropriate monitoring is arranged. Proactive communication between patients and healthcare professionals is fundamental to safe and effective weight management with Wegovy, ensuring that nutritional health is maintained alongside therapeutic weight loss goals.

If you experience any suspected side effects from Wegovy, including nutritional concerns, report them through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).

Frequently Asked Questions