Chapter 8 of 11

Supplements

When vitamins, electrolytes, probiotics or protein supplements can help — and what really matters first.

Many patients on GLP-1 medications may not need specialised supplements, electrolyte drinks, or probiotics — but some may benefit. The primary focus should always be on getting what your body needs through nutrient-dense, whole foods.

Vitamins and minerals

GLP-1 medications can reduce appetite and calorie intake by 16–39%. This may lead to inadequate intake of essential nutrients, especially when eating below ~1,200 kcal/day for women or ~1,800 kcal/day for men.

You may benefit if:

  • Your appetite is very low, and you're eating very little
  • Your daily intake is consistently low
  • You find it hard to eat a balanced, varied diet
  • You have known or suspected nutrient deficiencies
  • Blood tests show low levels of specific nutrients

Common deficiencies in obesity (pre-existing):

>50%
Vitamin D inadequate
up to 45%
Iron deficiency
2–8%
Vitamin B12 deficiency
up to 54%
Folate inadequate
>50%
Calcium & magnesium inadequate
24–28%
Zinc deficiency

What to focus on:

  • Prioritise nutrient-dense whole foodsFruits, vegetables, wholegrains, lean proteins, nuts, seeds
  • Consider a basic multivitamin-mineralIf appetite or overall calorie intake is low
  • Use specific supplementsVitamin D, calcium, B12 or iron, based on risk or confirmed deficiencies

Important to know

There isn't yet specific research on vitamin supplementation for people using GLP-1 medications. These recommendations are based on general nutrition guidance and what we know about common nutrient deficiencies.

Electrolyte drinks

In most cases, GLP-1 medications don't cause electrolyte imbalances that require supplements. They may help if you're unwell and losing fluids — for example with ongoing vomiting or diarrhoea.

Bottom line: most people don't need electrolyte drinks. Staying well hydrated and eating a balanced diet is usually enough.

Probiotics

There's no strong evidence to support the routine use of probiotics with GLP-1 medications. Most changes in gut health are likely due to diet and weight loss rather than the medication itself.

Bottom line: probiotics aren't routinely needed. A fibre-rich diet is the most effective and reliable way to support gut health.

Protein supplements

Some patients struggle to meet protein targets (1.2–1.6 g/kg/day) due to reduced appetite. Protein supplements such as shakes, bars, Greek yoghurt or cottage cheese can help bridge this gap.

Important to know

Protein supplementation alone does NOT prevent muscle loss. Structured resistance training is essential.

What really matters

Focus on these foundations — they make the biggest difference:

  • A nutrient-dense dietPrioritise whole foods over supplements
  • HydrationAim for 2–3 litres of water daily
  • Protein intakeAim for 1.2–1.6 g/kg/day from food sources first
  • Resistance trainingStrength-based training helps preserve muscle mass
  • Targeted supplements if neededBased on your intake or confirmed deficiencies

Signs you may need support — check in with your care team if you notice:

  • Fatigue beyond expected levels
  • Excessive hair loss
  • Skin flaking or itching
  • Muscle weakness
  • Poor wound healing
  • Unusual bruising