What Not to Take with B Complex: Navigating Interactions for Optimal Health

October 22, 2025 •

4 min read

While B-complex vitamins are vital for energy metabolism and overall health, approximately 20% of the population over 60 struggles to absorb vitamin B12, and certain substances can worsen this issue. Understanding what not to take with B complex is critical to ensure these essential nutrients are effectively absorbed and utilized by your body.

Quick Summary

Knowing which substances conflict with B complex supplements is essential for ensuring their effectiveness. Key interactions to be aware of include certain medications like acid inhibitors, high doses of vitamin C, excess alcohol, and specific minerals. Optimizing your intake schedule can prevent diminished absorption and negative health impacts.

Key Points

Separate Vitamin C: Take high doses of Vitamin C at least two hours apart from your B complex to prevent interference with B12 absorption.
Check Medications: Be cautious with gastric acid inhibitors, metformin, and anti-seizure drugs, as they can significantly impact B vitamin absorption.
Limit Alcohol: Excessive alcohol consumption damages the body's ability to absorb and utilize B vitamins, requiring supplementation in severe cases.
Balance Folic Acid Intake: Avoid excessively high doses of folic acid (B9), which can mask the symptoms of a serious vitamin B12 deficiency.
Take with Food: Taking B complex with food, preferably in the morning, can enhance absorption and help prevent stomach upset.
Avoid Raw Eggs: Frequent consumption of raw egg whites can lead to a biotin deficiency due to the presence of the protein avidin.
Consider Coffee and Tea: Some sources suggest separating B complex intake from coffee and tea to minimize absorption issues.

The B-complex family is a group of eight water-soluble vitamins crucial for various bodily functions, including energy production, nerve function, and cell metabolism. While they are generally safe, certain substances can interfere with their absorption or effectiveness. Being mindful of these interactions is a key part of responsible supplementation and a crucial aspect of a balanced nutrition diet.

Medications That Interfere with B Complex

Several common prescription and over-the-counter medications can negatively impact the absorption or metabolism of B vitamins, especially B12.

Gastric Acid Inhibitors: Medications used to reduce stomach acid, such as omeprazole (Prilosec) and lansoprazole (Prevacid), can hinder the absorption of vitamin B12 by slowing the release of hydrochloric acid needed to release B12 from food. Taking B complex supplements with these medications might reduce their efficacy. Some antacids should also be separated from B complex injections by at least 2 hours.
Metformin: This diabetes medication is known to lower the body's ability to absorb vitamin B12. For long-term users, regular monitoring of B12 levels is often recommended.
Anti-seizure Medications: Drugs used to treat epilepsy, such as phenytoin, can lower levels of vitamins B6 and B9 (folic acid), and affect B12 absorption.
Certain Antibiotics: Some antibiotics can interfere with B vitamin absorption. For instance, aminosalicylic acid can impact B12 absorption.
Bile Acid Sequestrants: Medications like cholestyramine, used to lower cholesterol, can interfere with B12 absorption.
Warfarin: Some formulations of B complex should not be taken with this anticoagulant.

Vitamins and Minerals with Potential Conflicts

While combining vitamins is common, certain pairings can cause issues, especially in high doses.

High-Dose Vitamin C: Taking a mega-dose of vitamin C (more than 500mg) at the same time as vitamin B12 can potentially decrease B12's availability. To avoid this, experts recommend separating the intake of these two supplements by at least two hours.
High-Dose Folic Acid (B9): High supplemental doses of folic acid can mask a vitamin B12 deficiency. This is a serious concern, as an undiagnosed B12 deficiency can lead to irreversible nerve damage over time.
Minerals and Absorption: Some minerals can influence B vitamin uptake. For example, calcium can form a chelate with riboflavin (B2), decreasing its absorption. Also, very high zinc intake might reduce magnesium absorption, which is important for activating thiamine (B1).

Food and Drink to be Mindful of

Beyond medications, daily dietary choices can impact how your body processes B vitamins.

Excessive Alcohol: Chronic and excessive alcohol consumption is a significant concern, as it directly impairs the absorption and storage of several B vitamins, including B1 (thiamine), B12, and B9 (folate). Alcohol can damage the stomach and intestinal lining, reducing the ability to absorb nutrients.
Coffee and Tea: Some advice suggests avoiding tea and coffee within two hours of taking your supplement, as the tannins and caffeine might interfere with absorption.
Raw Egg Whites: Regularly consuming large quantities of raw egg whites can induce biotin (B7) deficiency. Raw egg whites contain a protein called avidin, which can inhibit biotin absorption.

Understanding B Vitamin Interactions: A Comparison


Substance to Avoid/Limit	Reason for Conflict	Recommended Practice
High-Dose Vitamin C (>500mg)	Can degrade vitamin B12, reducing its absorption.	Take supplements at least 2 hours apart to minimize interaction.
Gastric Acid Inhibitors	Reduce stomach acid, which is needed to properly release and absorb vitamin B12 from food.	Consult a doctor; dosage or timing of B complex may need to be adjusted.
Excessive Alcohol	Damages the gut lining and impairs the absorption and storage of B vitamins.	Limit alcohol intake to support better B vitamin status.
High-Dose Folic Acid (B9)	Can conceal the signs of a vitamin B12 deficiency, delaying a crucial diagnosis.	Follow recommended dosages and test your B12 levels if you're taking high-dose B9.
Raw Egg Whites	Contain avidin, a protein that can prevent biotin (B7) absorption.	Ensure eggs are cooked to denature avidin; eat raw eggs sparingly.

Best Practices for Maximizing B Complex Absorption

For most people, taking a B complex supplement is straightforward, but a few best practices can help. Consider taking your supplement in the morning to leverage the energy-boosting effects without disrupting your sleep. Taking it with food can also help minimize nausea or other stomach upset, which can sometimes occur on an empty stomach. Choosing a form of the vitamin that is more bioavailable, such as methylcobalamin for B12, can also enhance effectiveness. Ultimately, a balanced diet remains the best source of nutrients, and supplements should complement, not replace, a healthy eating plan.

Conclusion

While B complex supplements are a valuable tool for supporting energy levels and overall well-being, their efficacy can be compromised by certain medications and lifestyle choices. By understanding what not to take with B complex, you can avoid potential conflicts with stomach acid-reducing drugs, high-dose vitamin C, and excessive alcohol. Always consult with a healthcare provider before starting or changing any supplement regimen, especially if you are on medication or have pre-existing health conditions, to ensure your approach is safe and effective.

Mayo Clinic is a trusted source for information on dietary supplements and interactions.

Frequently Asked Questions

Yes, you can generally take B complex and Vitamin C together, as both are water-soluble. However, high doses of Vitamin C (over 500mg) taken at the same time as Vitamin B12 might reduce B12 absorption. To be safe, some experts recommend separating them by a couple of hours.

Excessive and chronic alcohol consumption can significantly deplete B vitamin levels in the body and impair absorption. While occasional, moderate drinking is unlikely to cause a problem, heavy drinkers are at a higher risk of developing B vitamin deficiencies.

Yes, the diabetes medication metformin has been shown to decrease the body's ability to absorb vitamin B12. Long-term use of metformin may lead to a B12 deficiency, so patients should consult their doctor about monitoring levels and potentially supplementing.

While B vitamins are water-soluble and can be absorbed without food, some people experience nausea or stomach upset when taking them on an empty stomach. Taking them with a meal, particularly breakfast, can improve absorption and minimize digestive discomfort.

Excessively high supplemental doses of folic acid (B9) can mask the symptoms of a vitamin B12 deficiency, which can be dangerous. An undiagnosed B12 deficiency can lead to severe neurological problems over time.

Several medications can interact with B complex, including gastric acid inhibitors (like omeprazole), metformin, anti-seizure drugs (like phenytoin), and certain antibiotics. If you are on medication, it is crucial to consult your healthcare provider before taking supplements.

For optimal absorption, some sources suggest avoiding tea, coffee, and dairy products for at least two hours around the time of supplementation. Excessive alcohol intake should be avoided as it hinders B vitamin absorption. Also, raw egg whites can inhibit biotin absorption.