Supplement·Interactions·Reviewed June 9, 2026
Vitamin B9 interactions.
Vitamin B9 has 17 documented interactions in the NutriStack database: 8 that need timing or caution and 9 that work synergistically. The full list, with what each pairing does, is below.
Vitamin B9 at a glance.
A quick, data-grounded summary. The full table is below.
Vitamin B9 has 17 documented interactions in the NutriStack database: 8 that need timing or caution and 9 that work synergistically. The full list, with what each pairing does, is below.
Everything that interacts with vitamin b9.
Every supplement and medication in the NutriStack database with a documented interaction with this substance, highest-severity first. Open any pair for the mechanism and sources.
| Substance | Interaction | What happens |
|---|---|---|
| Carbamazepine | Caution | Carbamazepine reduces folate levels by inhibiting intestinal absorption and increasing hepatic folate catabolism. Folate deficiency can cause... details → |
| Elderberry Zinc Lozenges | Caution | High-dose elderberry zinc lozenges (>40mg) may impair folate absorption by inhibiting the folate conjugase enzyme in the gut. |
| Lamotrigine | Caution | Lamotrigine is a folate antagonist that inhibits dihydrofolate reductase. Long-term use may reduce folate levels. However, folate supplementation... details → |
| Phenytoin | Caution | Phenytoin depletes folate and folate supplementation may reduce phenytoin levels. This bidirectional interaction requires careful management. details → |
| Trimethoprim-Sulfamethoxazole | Caution | Trimethoprim is a folate antagonist that can lower host folate stores during prolonged therapy, particularly in patients with marginal folate... details → |
| Zinc | Caution | High-dose zinc (>40mg) may impair folate absorption by inhibiting the folate conjugase enzyme in the gut. |
| Zinc Carnosine | Caution | High-dose zinc carnosine (>40mg) may impair folate absorption by inhibiting the folate conjugase enzyme in the gut. |
| Zinc Picolinate | Caution | High-dose zinc picolinate (>40mg) may impair folate absorption by inhibiting the folate conjugase enzyme in the gut. |
| Combined Oral Contraceptive | Synergy | A systematic review and meta-analysis of 17 studies found that women using combined oral contraceptives had significantly lower serum and red-cell... details → |
| Methotrexate | Synergy | Vitamin B9 supplementation reduces common methotrexate side effects such as mouth sores, nausea, elevated liver enzymes, and blood-count problems in... details → |
| Methylcobalamin | Synergy | B9 (folate) and B12 work together in the methionine cycle. B12 deficiency can be masked by high folate intake. details → |
| Sulfasalazine | Synergy | Sulfasalazine can reduce folate absorption and inhibit folate-dependent enzymes. Most people do not develop severe deficiency, but risk rises with... details → |
| Valproic Acid | Synergy | Vitamin B9, usually as folic acid, has human evidence as an adjunct to sodium valproate in acute mania and is also clinically relevant because... details → |
| Vitamin B12 | Synergy | B9 (folate) and B12 work together in the methionine cycle. B12 deficiency can be masked by high folate intake. details → |
| Vitamin B6 | Synergy | B6 is required for the conversion of serine to glycine, which generates 5,10-methyleneTHF needed for folate-dependent one-carbon metabolism. |
| Vitamin C | Synergy | Vitamin C protects folate from oxidative degradation and helps maintain it in its reduced, active form. |
| Vitamin C Liposomal | Synergy | Vitamin C Liposomal protects folate from oxidative degradation and helps maintain it in its reduced, active form. |
The full vitamin b9 profile.
Benefits, dosing by goal, forms, and the cited evidence for this supplement.
Common vitamin b9 questions.
Quick answers drawn from the table above.
What interacts with Vitamin B9?
In the NutriStack database, Vitamin B9 has 17 documented interactions with other supplements and medications. The most notable include Carbamazepine, Elderberry Zinc Lozenges, Lamotrigine, Phenytoin, and Trimethoprim-Sulfamethoxazole.
What works well with Vitamin B9?
Vitamin B9 pairs synergistically with Combined Oral Contraceptive, Methotrexate, Methylcobalamin, Sulfasalazine, and Valproic Acid in the NutriStack database. Synergy still depends on dose and timing; open any pair for the detail.
Can you take Vitamin B9 with Carbamazepine?
NutriStack classifies the Vitamin B9 and Carbamazepine pairing as caution: Carbamazepine reduces folate levels by inhibiting intestinal absorption and increasing hepatic folate catabolism. Folate deficiency can cause megaloblastic anemia.... Low-dose folate supplementation (400-1000mcg/day) is generally recommended during carbamazepine therapy. Avoid high-dose folate (>5mg) as it may...
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