What Vitamins to Take on Ozempic: Navigating Your Nutrient Needs on a Weight Loss Journey

Last reviewed: July 2, 2026

Last updated: July 2, 2026

Written by: Jay Hastings, CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

This article is part of the PlexusDx Education Hub — science-backed guidance on GLP-1 medications, metabolic health, and precision weight management.

When you start semaglutide therapy, your digestive system undergoes significant changes that can impact nutrient absorption and utilization. GLP-1 medications slow gastric emptying, meaning food stays in your stomach longer, which affects how your body processes vitamins and minerals. PlexusDx patients benefit from understanding these metabolic shifts to optimize their supplementation strategy and protect long-term health.

How Semaglutide Affects Nutrient Absorption

Semaglutide works by slowing the rate at which food moves through your digestive tract. This delayed gastric emptying can reduce the efficiency of nutrient absorption, particularly for water-soluble vitamins like B12, folate, and vitamin C. Additionally, when you eat significantly less food—a natural result of appetite suppression—your total micronutrient intake decreases unless you intentionally choose nutrient-dense options.

Research shows that patients on GLP-1 therapy often experience reduced intrinsic factor production in the stomach, which is essential for B12 absorption. This makes B12 supplementation or monitoring especially important, even though semaglutide doesn't directly block absorption. Iron absorption may also be compromised due to lower stomach acid production and reduced food volume, potentially requiring supplemental iron or more frequent monitoring.

Critical Vitamins and Minerals During Semaglutide Treatment

Vitamin B12 stands out as the most important nutrient to monitor on semaglutide. This vitamin supports energy production, nerve function, and red blood cell formation—all crucial during weight loss when your body is under metabolic stress. Monthly B12 injections or high-dose oral supplements (1,000 mcg or higher) are often recommended for patients on GLP-1 therapy, though individual needs vary based on your genetic predisposition to absorption challenges.

Calcium, vitamin D, and iron deserve equal attention because semaglutide's appetite suppression typically reduces intake of fortified foods and animal proteins where these nutrients concentrate. Calcium supports bone health during rapid weight loss, vitamin D enhances calcium absorption and immune function, and iron prevents fatigue and supports oxygen transport. PlexusDx patients can reference their Precision Peptide Genetic Test results, which map 14 nutrient pathways including key variants in iron metabolism and calcium handling genes, to personalize their supplementation strategy.

Timing and Dosing Strategies for Supplements on Semaglutide

Taking supplements at the right time maximizes their effectiveness when your digestion is slowed by semaglutide. Water-soluble vitamins like B-complex and vitamin C absorb best when taken with food, ideally during your largest meal of the day when stomach acid is highest. Fat-soluble vitamins (A, D, E, K) also require dietary fat for absorption, so pair them with a meal containing healthy fats like olive oil or nuts.

Separate calcium supplements from iron supplements by at least two hours, as they compete for absorption. B12 supplements should be taken on an empty stomach or sublingually for optimal absorption, bypassing the gastric pathway that semaglutide affects. Work with a healthcare provider to establish a personalized supplement schedule, as high-dose supplementation without monitoring can lead to nutrient imbalances or interactions with semaglutide's effects on gut hormones.

Personalization Through Genetic Insight and Blood Work

Not everyone responds to semaglutide the same way, and nutrient needs vary significantly based on individual genetics and metabolism. PlexusDx Precision Peptide Genetic Test identifies your genetic variants in nutrient absorption pathways, including genes that influence iron metabolism (HAMP, TFR2), calcium homeostasis (CASR, VDR), and B12 handling (TCN2, MTHFR). Understanding your genetic predispositions allows you to anticipate nutrient risks before they develop into deficiencies.

Regular blood work during your first three to six months of semaglutide therapy provides a baseline for your nutrient status. Annual or semi-annual testing thereafter helps track vitamin B12, folate, iron (ferritin and TIBC), calcium, and vitamin D levels. PlexusDx patients starting Semaglutide Injection at $189/mo (or $149/mo on the 6-month plan) can add the Precision Peptide Genetic Test for $298 after their first month, integrating genetic insights into their personalized supplementation plan without increasing their ongoing medication cost—because your dose may go up, but your price won't.

How Your Genetics Relate to GLP-1 Pathways

Not everyone responds to GLP-1 medications the same way. Genetic variants — including GIPR rs1800437, FTO rs9939609, and MC4R rs17782313 — relate to the biological pathways these medications act on. These are pathway-level associations only and do not predict how much weight you will lose or how you will respond to any specific medication. PlexusDx maps 14 pathways, 49 peptides, and 150+ genetic insights so you and your provider can see how your genes relate to these pathways. It does not recommend, prescribe, or determine which medication, dose, or peptide is right for you. The PlexusDx Precision Peptide Genetic Test ($298) gives you and your provider pathway-level genetic context to support a more personalized conversation. Genetics is a guide, not a guarantee.

Access Personalized GLP-1 Care Through PlexusDx

PlexusDx offers seven prescription GLP-1 protocols to all 50 states — no membership, no insurance required, async intake or live consult. The Semaglutide Injection is $189/mo month-to-month, or from $149/mo on the 6-month plan. Medications are dispensed from licensed 503A compounding pharmacies following strict quality and safety standards. Add a Precision Peptide Genetic Test for $298 to personalize your protocol from day one.

Frequently Asked Questions

Do I need to take vitamins while on semaglutide?

Supplementation becomes necessary for most patients on semaglutide due to reduced food intake and slower nutrient absorption. At minimum, B12 monitoring and supplementation are strongly recommended. PlexusDx providers can review your individual needs based on your baseline blood work and genetic risk factors.

Can I take my regular multivitamin with semaglutide?

A standard multivitamin may not provide therapeutic doses of the nutrients most affected by semaglutide, particularly B12 and iron. Most patients benefit from targeted, higher-dose supplements of critical nutrients rather than relying on a one-size-fits-all multivitamin formula. Timing matters too—take multivitamins with food to maximize absorption in your slowed digestive tract.

How much does semaglutide cost at PlexusDx, and does it include nutrient guidance?

PlexusDx Semaglutide Injection is $189/mo month-to-month (or $149/mo on the 6-month plan) with no membership fees or insurance required, and it's HSA/FSA eligible. While the medication itself doesn't include supplementation, PlexusDx patients can add the Precision Peptide Genetic Test for $298 (after month one) to identify personalized nutrient vulnerabilities and optimize their supplementation strategy.

Is B12 supplementation necessary if I'm on semaglutide?

Clinical evidence shows that GLP-1 users have increased risk of B12 deficiency due to reduced intrinsic factor and lower food volume intake. Most healthcare providers recommend either monthly B12 injections, weekly high-dose oral supplements (1,000+ mcg), or sublingual formulations during semaglutide therapy to prevent energy loss, cognitive fog, and neuropathy.

How does the Precision Peptide Genetic Test help with supplement choices on semaglutide?

No — the Precision Peptide Genetic Test does not predict your response to Ozempic or any specific medication. It analyzes pathway-level variants (GIPR, FTO, and MC4R) that relate to the biology involved, offering context for a conversation with your provider rather than a prediction.

Related Reading

• Ozempic For Weight Loss 2
• Average Weight Loss On Ozempic
• Weight Loss Drugs Like Ozempic
• Ozempic Weight Loss Before And After Pictures

Pricing and availability current as of July 2026. Compounded GLP-1 medications are not FDA-approved drug products; they are prepared by licensed compounding pharmacies under federal compounding regulations. Compounded semaglutide and tirzepatide are not the same as Wegovy, Ozempic, Zepbound, or Mounjaro. This article is for informational purposes only and does not constitute medical advice. Consult a licensed healthcare provider before starting, stopping, or changing any medication.

Return to the PlexusDx Education Hub for more evidence-based resources on GLP-1 therapy, metabolic health, and personalized weight management.

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.