Introduction: why supplements matter during GLP-1
GLP-1 medication such as Ozempic (semaglutide), Wegovy and Mounjaro (tirzepatide) powerfully suppresses appetite. That's exactly the point — you eat less and lose weight. But eating less also means a lower intake of protein, vitamins and minerals. With a sharply reduced calorie intake you risk deficiencies, even if you try to eat healthily.
Supplements are not a miracle cure and never replace a good diet. But during GLP-1 treatment, a few well-chosen supplements do play an important protective role: they help preserve muscle mass, keep bones strong, prevent fatigue and ease side effects such as nausea and constipation.
This guide explains for each supplement whether, why and how much you need during a GLP-1 journey. Important: this is educational information. Which supplements are right for you depends on your blood values, diet and medical situation. At Go Leaner we determine this based on blood testing and the assessment of a registered physician.
Table of Contents
- • Why supplements matter during GLP-1
- • Protein: the top priority
- • Vitamin B12
- • Vitamin D and calcium
- • Magnesium
- • Omega-3 fatty acids
- • Multivitamin as a safety net
- • Fiber for constipation
- • Electrolytes and hydration
- • What to avoid
- • Practical intake schedule
- • Guidance at Go Leaner
- • Frequently asked questions
Why supplements matter during GLP-1
Smaller portions increase the risk of deficiencies
During GLP-1 treatment you eat on average 30 to 50% less than before. Your stomach fills faster, gastric emptying is slowed and appetite drops sharply. As a result you automatically take in fewer nutrients. With a large calorie deficit, intake of protein, iron, B vitamins, calcium and vitamin D can fall below the recommended level.
On top of that, rapid weight loss adds strain. Your body breaks down fat tissue, but without enough building blocks it also breaks down muscle. Bone loss can accelerate with prolonged low-calorie eating. Several supplements act as a targeted safety net here: they fill precisely the gaps created by reduced intake.
Not everyone needs all supplements. Someone still eating relatively varied meals needs less supplementation than someone with strong appetite suppression and tiny portions. That's why blood testing is the foundation: measure to know. Based on that we advise specifically rather than prescribing everything by default.
1. Protein: the top priority
Protecting muscle mass comes first
If there's one supplement priority during GLP-1, it's protein. During rapid weight loss, up to 30% of the weight lost can be muscle mass if you don't get enough protein. Muscle loss slows your metabolism and increases the chance of yo-yo regain after treatment.
The recommendation during weight loss is 1.6 to 2.2 grams of protein per kilogram of body weight per day. With the small portions GLP-1 causes, that's often hard to reach through regular meals. A protein shake (whey or plant-based, 20-30 grams per serving) is therefore not a luxury but a practical tool: it takes little volume and counts fully.
Prefer a whey isolate or a plant-based blend without added sugars. Spread your protein across the day (25-35 grams per moment) rather than all at once. Read more in our detailed guide to protein for weight loss. Protein for weight loss.
2. Vitamin B12
Energy, nervous system and blood formation
Vitamin B12 is found mainly in animal products (meat, fish, eggs, dairy). Because you eat less on GLP-1 — and some people lose their appetite for meat in particular — B12 intake can drop. A deficiency shows up as fatigue, concentration problems, tingling and anemia.
Vegetarians, vegans and people using metformin (often with type 2 diabetes, alongside GLP-1) are at extra risk. A maintenance dose of 100-250 micrograms per day, or periodic monitoring of blood values, is sensible. With a confirmed deficiency a higher dose or injection may be needed — the physician decides.
3. Vitamin D and calcium
Protecting bone health during weight loss
Vitamin D is a concern in the Netherlands anyway due to limited sunlight; a large share of the population has too low a level. During weight loss bone protection is extra important, because prolonged low-calorie eating can accelerate bone loss. Vitamin D ensures you absorb calcium properly.
A common maintenance dose is 10-25 micrograms (400-1000 IU) of vitamin D per day, higher with a confirmed deficiency. Calcium is ideally obtained from food (dairy, green vegetables); if that fails due to small portions, a supplement of 500-1000 mg can help. Vitamin D and calcium work together — which is why they're often combined.
4. Magnesium
Muscles, sleep and against cramps
Magnesium is involved in hundreds of processes in the body: muscle function, energy production, sleep and nerve function. With reduced food intake and during weight loss, magnesium status can drop. Symptoms of a deficiency are muscle cramps, fatigue, poor sleep and irritability.
Magnesium can also help with constipation — a common GLP-1 side effect. Magnesium citrate or bisglycinate (200-400 mg per day, preferably in the evening) is well absorbed and gentle on the stomach. With kidney problems, consult your physician first.
5. Omega-3 fatty acids
Anti-inflammatory and cardiovascular health
Omega-3 fatty acids (EPA and DHA, from oily fish or fish/algae oil) support cardiovascular health, are mildly anti-inflammatory and may help preserve muscle mass during weight loss. Many people get too little because they eat little oily fish.
A dose of 1000-2000 mg of combined EPA/DHA per day is common. Algae oil is a complete plant-based alternative to fish oil. Take omega-3 with a meal for best absorption and to limit burping (a known complaint).
6. Multivitamin as a safety net
Broad coverage with sharply reduced intake
A good multivitamin is not a replacement for targeted supplements, but acts as a broad safety net during heavily reduced food intake. It covers small deficiencies of vitamins and minerals you might just miss due to small portions — like zinc, folic acid, iron and the B vitamins.
Choose a multivitamin without excessive mega-doses. More is not better: fat-soluble vitamins (A, D, E, K) can accumulate. One tablet per day with a meal is enough. With a specifically confirmed deficiency, targeted supplementation is always more effective than a general multi.
7. Fiber for constipation
Against a common GLP-1 side effect
Constipation is one of the most reported side effects of GLP-1 medication, because bowel transit slows and you eat less (fiber-rich) food. A fiber supplement such as psyllium can normalize bowel movements. Start low and build up slowly to avoid bloating.
Crucial with fiber: drink enough water. Fiber without fluid actually worsens constipation. Take psyllium (5-10 grams per day) with a large glass of water, separate from your medication and other supplements, because fiber can affect absorption.
8. Electrolytes and hydration
Against fatigue, headache and dizziness
Because you eat and drink less, you also take in less sodium, potassium and magnesium. This can cause fatigue, headache, dizziness on standing and muscle cramps — especially in the first weeks and during dose increases. Conscious hydration is therefore important.
Aim for 1.5-2 liters of fluid per day. A sugar-free electrolyte solution can help, especially if you exercise or sweat a lot. Beware of ready-made sports drinks: they often contain a lot of sugar. Choose a variant without added sugars.
9. What to avoid
Not everything 'natural' is safe
Avoid 'fat burners', slimming teas and herbal supplements with stimulants (caffeine bombs, synephrine, yohimbine). Combined with the appetite suppression of GLP-1 these can cause palpitations, high blood pressure and dehydration. They add nothing to a medically supervised journey.
Also be careful with high doses of single vitamins without a confirmed deficiency, and with herbs that affect blood sugar or blood pressure (such as berberine) if you already use medication. Always tell your treating physician which supplements you use — even 'natural' products can interact.
10. Practical intake schedule
An example of a simple daily layout
A workable schedule prevents supplements from interfering with each other's absorption. An example (always tailor to your blood values and physician):
| Moment | Supplement |
|---|---|
| Morning (with breakfast) | Multivitamin, vitamin D, omega-3, B12 |
| During the day | Protein shake (if protein goal not met through food) |
| Separate moment, with plenty of water | Fiber (psyllium) — apart from medication and other supplements |
| Evening | Magnesium (relaxes muscles, supports sleep) |
11. Guidance at Go Leaner
At Go Leaner we don't look at supplements by default, but specifically. During intake we perform extensive blood testing to map deficiencies in vitamin D, B12, iron and other values. Based on that the registered physician advises which supplementation is useful for you — no more, no less.
Throughout your journey we periodically monitor your values and adjust the advice. Our dietitian also helps you get as many nutrients as possible from real food, so supplements remain a complement rather than a replacement. This is how you combine safe weight loss with preserving your health.
Frequently asked questions about supplements with GLP-1
Related articles
- Protein for weight loss: complete guide
- Nutrition during GLP-1 medication
- GLP-1 side effects and how to limit them
- GLP-1 complete guide
This information is educational and does not replace personal medical advice. Which supplements are suitable for you depends on your blood values, diet, medication and health. Always consult a registered physician before starting supplements, especially with kidney problems, pregnancy or existing medication.