Weight loss injections like GLP-1 receptor agonists (e.g., semaglutide, liraglutide, tirzepatide) are gaining popularity due to their ability to regulate appetite, improve insulin sensitivity, and support sustained fat loss. However, these injections can also alter nutrient absorption, appetite levels, and digestion, leading to potential vitamin and mineral deficiencies. Ensuring optimal supplementation with any injectable weight loss treatment is crucial for health, energy, and long-term success.
Weight loss injections like Mounjaro can be incredibly effective in helping you shed excess weight, they can also change your eating habits and how your body absorbs nutrients. As your appetite decreases and your portions become smaller, you may find it more difficult to get all the essential vitamins and minerals your body needs to function at its best.
That’s where targeted supplementation comes in – helping to fill any nutritional gaps, support your metabolism, and keep you feeling energised and well throughout your weight loss journey.
Reduced Appetite and Nutrient Intake
Weight loss injections commonly reduce your hunger, which can lead to lower food consumption. This often results in fewer calories and fewer micronutrients being consumed overall. Over time, this can increase the risk of deficiencies in essential vitamins and minerals.
Changes in Digestion and Absorption
Some weight loss injections slow gastric emptying, meaning food moves more slowly through the digestive system. While this helps with feeling full, it may also impact how nutrients are absorbed in the gut, especially fat-soluble vitamins (A, D, E, K) and certain minerals.
Metabolic Demand During Weight Loss
Your body’s metabolic activity increases during fat loss, especially when combined with exercise. This increases the demand for nutrients to support energy production, hormone balance, and muscle function.
B12 plays a vital role in energy production, DNA synthesis, and nervous system health.
Risk of deficiency: Weight loss injections, particularly those involving GLP-1 agonists, can impair B12 absorption.
Recommended form: Methylcobalamin or cyanocobalamin (oral or injectable).
Dosage: 1,000 mcg daily or weekly under guidance, depending on lab levels.
Supports immune function, bone density, and mental health.
Deficiency link: A large percentage of adults are already deficient in Vitamin D, and reduced dietary intake worsens it.
Recommended form: D3 (cholecalciferol).
Dosage: 1000 units daily; adjust based on blood test results.
Involved in over 300 biochemical reactions, including muscle contraction, nerve signalling, and sleep regulation.
Deficiency signs: Muscle cramps, fatigue, anxiety, insomnia.
Best forms: Magnesium glycinate or citrate.
Dosage: 200–400 mg daily.
Supports cardiovascular health, reduces inflammation, and aids cognitive function.
Deficiency risk: Lower intake of oily fish and fats due to reduced appetite can lead to low omega-3 levels.
Recommended source: High-quality fish oil or algal oil (for vegans).
Dosage: 1,000–2,000 mg of combined EPA/DHA daily.
Iron is essential for oxygen transport and preventing fatigue.
Deficiency signs: Tiredness, dizziness, pale skin, cold hands and feet.
Consider testing: Before supplementing, too much iron is harmful.
Dosage: If needed, 18 mg–27 mg daily with vitamin C for better absorption.
A good quality multivitamin ensures you get a broad spectrum of essential micronutrients, particularly when your diet is restricted.
What to look for: Activated forms (like methylated B vitamins), iron (if needed), iodine, zinc, selenium.
Daily use: One-a-day formula can help bridge dietary gaps.
Why: GLP-1s slow digestion, sometimes causing constipation or bloating. Fibre supports healthy gut function and regulates blood sugar.
Sources: Psyllium husk, inulin, or partially hydrolysed guar gum (PHGG).
Dosage: 5–10 grams daily with plenty of water.
Why: Changes in gut motility and digestion can affect your microbiome.
Benefits: Improved digestion, reduced bloating, enhanced immune function.
Suggested strains: Lactobacillus acidophilus, Bifidobacterium lactis.
Dosage: 10–30 billion CFUs daily.
Why: Essential for converting food into usable energy (ATP), especially beneficial during calorie restriction.
Form: Ubiquinol is better absorbed than ubiquinone.
Dosage: 100–200 mg daily.
Ask your GP or healthcare provider for routine blood work: B12, vitamin D, iron, magnesium, thyroid function. Personalised supplementation is more effective and prevents overdose.
Vitamins A, D, E, and K are better absorbed with dietary fat. Take with a small amount of healthy fat (e.g., avocado, nuts, olive oil).
Don’t take everything at once. Iron and calcium compete for absorption.
Magnesium and B vitamins are best in the evening (calming effect)
Look for third-party tested supplements, ideally free from unnecessary fillers, artificial colours, or sugars.
Lifestyle Considerations for Nutrient Optimisation
Balanced Nutrition Still Matters
While injections suppress appetite, try to eat nutrient-dense meals that prioritise:
– Lean proteins (chicken, fish, tofu)
– Leafy greens and coloured veg
– Whole grains (quinoa, oats)
– Healthy fats (nuts, seeds, olive oil)
Aim for at least 2 litres of water daily to support detoxification, digestion, and reduce the risk of constipation and slowed gut motility.
To maintain optimal hydration:
– Use a sugar-free electrolyte powder or drink with balanced minerals.
– Include sea salt or Himalayan salt in your meals.
– Eat foods rich in potassium (like avocados, spinach, or bananas) when your appetite permits.
Proper hydration with electrolytes ensures your body functions smoothly during the fat loss process and helps prevent the common side effects of injectable treatments.
Combine weight loss injections with resistance training to maintain muscle, which also improves insulin sensitivity and long-term weight control.
Combining supplementation with your weight loss injections ensures better energy, mood, digestion, and long-term success. You’re not just losing weight—you’re building a sustainable foundation of health. Always consult a healthcare professional for personalised advice and adjust your supplement regime based on symptoms and lab results.
Medically reviewed by
Superintendent Pharmacist
If you are experiencing mounjaro constipation, you are not alone. Constipation is a well recognised side effect of Mounjaro and other GLP-1 based weight loss treatments. For many people, it is mild and temporary. For others, it can be uncomfortable enough to affect daily life and confidence in continuing treatment. From the perspective of The […]
If you are researching the best weight loss capsules, you are not alone. Many people begin their weight loss journey by looking for tablets or capsules before considering injectable treatments. At The Care Pharmacy, we support patients across the UK with honest, clinically led advice so they can understand which options are most effective, safe, […]
Many people exploring prescription weight loss treatments ask the same question. Is Saxenda right for me, or are there other options that may work better? With increasing awareness of injectable weight loss treatments, it is important to understand how Saxenda compares with other injections and with traditional weight loss methods. This guide explores how Saxenda […]
Interest in weight loss injections UK services has grown rapidly as more people look for clinically supported ways to manage their weight. At The Care Pharmacy, we provide regulated online access to private weight loss injections, supported by clinical assessment, ongoing review, and clear expectations around results and safety. If you are considering private treatment […]
Mounjaro can cause diarrhoea because tirzepatide slows digestion and changes gut motility, leading to more frequent bowel movements as your body adjusts. Diarrhoea is a common and usually short-term side effect, especially in the first few weeks or after a dose increase. In this guide, you’ll understand the exact reasons diarrhoea can happen on Mounjaro […]
Mounjaro is now widely used for weight loss and type 2 diabetes, but with its growing popularity comes a common concern about how it fits into everyday life, especially when drinking alcohol. There’s no evidence of a reaction to drinking on Mounjaro, but it can cause some side effects like nausea and changes in blood […]
