Can I Take Folate with Low-Dose Naltrexone?

Folate (vitamin B9, including folic acid and L-methylfolate) and low-dose naltrexone (LDN, compounded naltrexone hydrochloride at roughly 1.5 to 4.5 mg nightly, distinct from the FDA-approved 50 mg naltrexone tablet used for opioid and alcohol use disorder) have no shared metabolic pathway, receptor target, or transporter. No published pharmacokinetic or pharmacodynamic interaction between the two has been reported, and the mechanisms each substance relies on do not overlap. That is the direct answer for a healthy adult taking standard-dose folate with compounded LDN.

The more useful question for most people asking this is not whether the combination is dangerous, but which form and dose of folate makes sense given why they are on LDN in the first place. Many people using off-label LDN do so for fibromyalgia, multiple sclerosis, inflammatory bowel disease, or PCOS, conditions that are independently associated with folate insufficiency or with MTHFR variants that change how folate should be dosed. That context, not a drug interaction, is where the real decision-making happens.

What LDN and folate each do

LDN. Compounded low-dose naltrexone is the same molecule sold at 50 mg under FDA-approved labeling for opioid and alcohol use disorder, prepared instead at a fraction of that dose. At low doses, naltrexone produces a brief opioid receptor blockade that appears to trigger a rebound increase in endogenous opioids. A second, mechanistically distinct pathway involves naltrexone's action on Toll-like receptor 4 (TLR4) on microglia and macrophages, which is the pharmacological rationale offered for off-label LDN use in fibromyalgia, multiple sclerosis, and inflammatory bowel disease. This off-label use is supported by small trials and observational reports rather than FDA-approved labeling, and effect sizes in the LDN literature are generally modest and not consistent across all conditions studied.

Naltrexone is metabolized hepatically to its active metabolite, 6-beta-naltrexol, largely independent of the CYP450 enzyme system that is responsible for most drug-supplement interactions. This is one reason the supplement-interaction profile of LDN is generally described as narrow.

Folate. Folate is the general term for the B9 vitamin family, including synthetic folic acid, the reduced active form L-methylfolate (5-MTHF), and folinic acid (leucovorin). Dietary folate and folic acid require enzymatic conversion, including the enzyme MTHFR, before they can donate methyl groups in the one-carbon cycle that supports DNA synthesis and homocysteine clearance. The CDC recommends 400 mcg of folic acid daily for women capable of pregnancy and 600 mcg during pregnancy, a standard, current public health recommendation (CDC folic acid recommendations, accessed 2025: https://www.cdc.gov/ncbddd/folicacid/recommendations.html).

Is there a direct interaction?

No. Folate is absorbed in the proximal small intestine through a dedicated transporter and is processed through DHFR and MTHFR enzymes. Naltrexone is absorbed by passive diffusion and metabolized through a separate hepatic pathway that does not depend on CYP450 induction or inhibition at low doses. Because the two substances do not compete for absorption, do not share metabolizing enzymes, and do not act on a common receptor or downstream pathway, no pharmacokinetic or pharmacodynamic interaction is expected on mechanistic grounds. This absence of a documented interaction reflects the lack of an identified mechanism rather than the existence of a dedicated LDN-folate interaction trial, and no such trial appears in the literature reviewed for this article.

This is the core, quotable finding of this page: folate and compounded low-dose naltrexone (1.5 to 4.5 mg nightly) act through separate absorption routes, separate metabolic enzymes, and separate biological targets, so no pharmacokinetic or pharmacodynamic interaction has been identified between them; this conclusion is based on mechanistic reasoning and the absence of reported cases, not on a dedicated interaction trial, and it applies to standard folate dosing rather than very high-dose folate regimens, which have their own independent considerations.

Evidence-status interaction assessment

Why the folate form matters more than the interaction question

For most LDN users without a known MTHFR variant, standard folic acid in the 400 to 800 mcg range, consistent with general dietary guidance, is adequate. The more consequential decisions are:

MTHFR status. People with reduced-function MTHFR variants convert folic acid to its active form less efficiently. In that group, L-methylfolate, which does not require MTHFR-dependent conversion, is a reasonable first-line choice, though whether to test for MTHFR at all is itself debated; professional genetics guidance has generally not recommended routine population screening for MTHFR variants in asymptomatic adults, reserving testing for specific indications such as recurrent pregnancy loss or a personal/family history of neural tube defects. Confirm current testing recommendations with a genetics or primary care clinician before ordering this test.

Methotrexate coadministration. Some patients on LDN for rheumatoid arthritis or Crohn's disease also take low-dose methotrexate, a folate antagonist. Concurrent folic or folinic acid supplementation to reduce methotrexate toxicity is a standard rheumatology practice, independent of LDN. LDN does not interfere with this protective effect because it does not act on the enzyme methotrexate targets (dihydrofolate reductase).

Absorption limitations. Active small-bowel inflammation, such as in uncontrolled Crohn's disease, or reduced gastric acid in older adults, can impair absorption of some folate forms. In these situations, L-methylfolate or folinic acid, which require fewer absorption-dependent conversion steps, may be preferred. This is a folate-absorption consideration, not an LDN interaction.

Pregnancy. Women using off-label LDN for PCOS-related ovulatory dysfunction or autoimmune conditions who are pregnant or trying to conceive should follow standard CDC folic acid guidance (600 mcg daily) and discuss any MTHFR-related dose adjustment with an obstetric provider. No evidence indicates LDN changes folate requirements in pregnancy, but LDN use in pregnancy itself is off-label and should be discussed directly with the prescribing clinician.

Dosing and timing

There is no pharmacologic reason to separate folate and LDN doses. LDN is conventionally taken at bedtime; folate is commonly taken in the morning with food. Taking both together is also acceptable.

• Adults without a known MTHFR variant: standard folic acid, 400 to 800 mcg daily, in line with general preventive nutrition guidance.
• Confirmed MTHFR reduced-function variant: L-methylfolate, roughly 400 to 1,000 mcg daily, is a reasonable starting point; doses above this range should involve prescriber input.
• Concurrent low-dose methotrexate: follow rheumatology guidance for folic or folinic acid dosing regardless of MTHFR status; this should be set by the prescribing clinician managing the methotrexate.
• Pregnant or planning pregnancy: at least 600 mcg folic acid daily per CDC guidance, adjusted with obstetric input if an MTHFR variant is known.

These are general starting points drawn from public health and rheumatology practice, not individualized dosing instructions, and a clinician or pharmacist should confirm the right choice given a person's full medication list and lab values.

What monitoring is reasonable

Routine lab monitoring is not required simply because someone takes folate with LDN. For patients with autoimmune or inflammatory conditions starting LDN, checking baseline serum folate and homocysteine can be useful because clinical symptoms alone do not reliably distinguish folate insufficiency from the underlying disease. An elevated homocysteine in the setting of normal folate should prompt a vitamin B12 check, since B12 is a required cofactor in the same methylation reaction. If L-methylfolate is started for a documented MTHFR variant, rechecking homocysteine after a few months is a reasonable way to confirm the supplement is working as intended, though the exact interval should be set by the ordering clinician.

Evidence boundary

Established: Folate and low-dose naltrexone are processed through separate absorption, metabolic, and receptor pathways, and no interaction has been reported in the literature reviewed. Standard folic acid dosing for general health, and folic acid coadministration with methotrexate, are supported by long-standing, accountable clinical guidance independent of LDN.

Plausible but unproven: That correcting folate insufficiency specifically improves LDN-treated symptoms such as fatigue or pain in fibromyalgia or MS. That LDN's anti-inflammatory mechanism and folate-supported methylation produce any measurable additive clinical benefit in humans.

Not established: Any claim of a specific numeric benefit from combining folate with LDN, or any claim that LDN changes folate requirements beyond what the underlying condition (inflammatory bowel disease, pregnancy, older age) already implies. Several precise figures reported in earlier drafts of LDN-supplement content (specific percentage reductions in enzyme activity, specific mean differences in serum folate between disease and control groups) could not be independently verified against a confirmed primary source for this review and have been left out rather than restated as fact. An editor or clinician with direct access to the primary literature should confirm any such figures before they are reintroduced.

When to contact your prescriber

Contact your prescriber or pharmacist if you develop new gastrointestinal symptoms after starting a folate supplement, if you notice mood changes after starting high-dose L-methylfolate (above roughly 1,000 mcg daily), particularly if you have a personal or family history of bipolar disorder, or if your pain or inflammatory symptoms change in a way that seems tied to the folate rather than to LDN dose. Seek urgent care for any signs of an allergic reaction, severe abdominal pain, or unexpected neurological symptoms, none of which are expected from this combination but all of which warrant evaluation rather than self-diagnosis.