Mounjaro (tirzepatide) whilst showing remarkable results for many users, rapid weight loss or dietary changes during treatment can lead to certain nutrient deficiencies. To stay balanced and healthy, it’s a good idea to consider adding specific vitamins and supplements to your routine.
Here’s a guide to what supplements may help support your health whilst using Mounjaro.

1. Multivitamin (Daily)

Why it’s helpful: When you’re losing weight quickly, especially if you’re eating less overall, you may not be getting enough essential vitamins and minerals from food alone. A high-quality multivitamin can help cover your nutritional bases.

What to look for:

• Iron (if you menstruate or have a known deficiency)
• B-complex vitamins
• Zinc, selenium, and magnesium
• Vitamin D3 and K2

PHS Recommends:

WeightWorld, Multivitamin tablets with 27 active multivitamins & minerals.
£23.99 (12 month supply) #paid link.

Inessa, Advanced multivitamin is a complete one-a-day multivitamin packed with antioxidants, B-complex, CoQ10, and more to promote optimal nutrition and overall health.
£26.99 (2 month supply) #paid link.

2. Vitamin B12

Why it’s helpful: GLP-1 receptor agonists like Mounjaro can sometimes interfere with nutrient absorption, particularly B12. A deficiency can lead to fatigue, weakness, and even neurological symptoms over time.

What to look for:

• Sublingual or methylcobalamin for better absorption
• Consider injections if blood levels drop significantly

PHS Recommends:

WeightWorld, Vitamin B12 tablets, 1000mcg B12 supplement, 450 methylcobalamin.
£7.49 (12 month supply) #paid link.

Thorne, Vitamin B12 in the active methylcobalamin form, supports cardiac function, sleep regulation, blood cell formation, and nerve function.
£19.79 (2 month supply) #paid link.

Cytoplan, Sublingual tablets with methylcobalamin and adenosylcobalamin, the most active forms of vitamin B12, provide rapid absorption.
£8.99 (2 month supply) #paid link.

3. Vitamin D + K2

Why it’s helpful: Vitamin D supports mood, immune function, and bone health—especially important if your diet or sun exposure has decreased. K2 helps direct calcium to the bones rather than arteries, working synergistically with D.

PHS Recommends:

WeightWorld, Vitamin D3 4000IU & vitamin K2 125μg (MK7) tablets.
£14.44 (8 month supply) #paid link.

Thorne, A convenient liquid supplement combining vitamin D and vitamin K for enhanced support of bone health, cardiovascular function, and immune system.
£24.29 (10 month supply) #paid link.

4. Magnesium

Why it’s helpful: Magnesium supports muscle function, sleep quality, and regular bowel movements—all of which can be disrupted during weight loss. Some users on Mounjaro report constipation, and magnesium can help relieve this naturally.

Best forms:
• Magnesium glycinate (gentle, supports sleep)
• Magnesium citrate (for occasional constipation)

PHS Recommends:

WeightWorld, Magnesium Citrate supplement 1480mg, providing 440mg high absorption elemental Magnesium.
£14.44 (4 month supply) #paid link.

Sport Supplies, Magnesium Glycinate supplement 1500mg & vitamin B6. High strength capsules, 1500mg of Magnesium providing 315mg elemental Magnesium (Bisglycinate), pure active ingredient.
£7.22 (2 month supply) #paid link.

Pure Encapsulations, Magnesium Citrate. Highly bioavailable magnesium chelate, a superior supplement renowned for its quick absorption and premium quality.
£31.49 (6 month supply) #paid link.

Pure Encapsulations, Magnesium Glycinate. Highly bioavailable magnesium chelate for sensitive individuals.
£22.49 (3 month supply) #paid link.

5. Probiotics

Why it’s helpful: Some users experience gastrointestinal side effects (bloating, nausea, or constipation) on Mounjaro. A good probiotic may support gut health and help reduce those symptoms over time.

Choose:

A multi-strain probiotic with at least 10 billion CFUs
Preferably one with Lactobacillus and Bifidobacterium strains

PHS Recommends:

WeightWorld, Bio cultures complex probiotics and prebiotics, 77 billion CFU, 20 live bacterial cultures, probiotic complex capsules (Lactobacillus Acidophilus, Gasseri, Rhamnosus & Reuteri).
£16.99 (1 month supply) #paid link.

Vilgain, Probiotics – a science-backed formula of 7 strains and 10 billion live cultures. Promotes a balanced microbiome while supporting digestion, immunity, and mood for better overall health.
£13.04 (2 month supply) #paid link.

6. Omega-3 Fatty Acids (Fish Oil)

Why it’s helpful: Omega-3s support cardiovascular health and may help reduce inflammation during weight loss. They also contribute to brain and joint health, which is important for anyone making lifestyle changes or increasing physical activity.

Dosage: 1,000–2,000 mg per day of combined EPA and DHA

PHS Recommends:

WeightWorld, Omega 3 fish oil, EPA & DHA, 1000mg Omega 3 fatty acids supplement.
£28.49 (12 month supply) #paid link.

Momentous, Omega 3 delivers a potent 1600mg of EPA and DHA in a 1:1 ratio, supporting heart health, brain function, and aiding muscle and joint recovery.
£46.34 (1 month supply) #paid link.

7. Electrolytes

Why it’s helpful: As you lose weight or reduce carb intake, your body may excrete more water and electrolytes (like sodium, potassium, and magnesium). This can lead to fatigue, headaches, or muscle cramps.

Solution:

Add a daily electrolyte supplement or drink
Look for options without added sugars or artificial dyes

PHS Recommends:

Phizz, Electrolytes, multivitamin & hydration tablets,18 vitamins & minerals, vitamin C, low calorie (orange flavour).
£12.75 (2 month supply) #paid link.

LMNT, Unlock peak hydration, performance, and delicious flavours with LMNT, a clean zero sugar electrolyte mix with a powerful science-backed blend of sodium, magnesium, and potassium.
£17.09 (12 serving trial pack) #paid link.

Bodyhealth, A perfectly balanced, easy to use, and delicious electrolyte drink formula fortified with Perfect Amino to help rebuild muscle and improve endurance.
£24.29 (1 month supply) #paid link.

Bonus: Fiber Supplement

Why it’s helpful: Mounjaro slows digestion, which can cause constipation. If your diet is lower in fiber due to reduced appetite, a supplement like psyllium husk or inulin can help.

PHS Recommends:

New Leaf, Fibre Supplement 4000mg Psyllium Husk with Acidophilus – High Strength.
£11.86 (2 month supply) #paid link.

FiberMend, Nurture your gut health and cultivate beneficial gut bacteria with a nourishing dose of prebiotic fibre.
£31.49 (1 month supply) #paid link.

Optibac, For anyone looking to buy a natural option for supporting digestive health and regularity.
£17.99 (1 month supply) #paid link.

Final Tips:

Always talk to your healthcare provider before starting any new supplements, especially if you have preexisting conditions or take other medications.

Have your labs monitored regularly to ensure optimal nutrient levels and adjust supplements as needed.

Prioritize whole foods rich in these nutrients as your appetite allows—supplements should complement, not replace, a nutrient-dense diet.

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