Leucovorin

vitaminfolate
Best with a meal

What is it

Leucovorin (folinic acid, 5-formyltetrahydrofolate) is a reduced, biologically active form of folate available as a prescription pharmaceutical. Unlike folic acid, it does not require reduction by dihydrofolate reductase (DHFR) to become metabolically active, which is the basis for its use as a rescue agent after methotrexate and as a biomodulator of fluorouracil chemotherapy. It is a synthetic drug, not a dietary supplement.

Evidence for 4 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Methotrexate rescue after high-dose chemotherapy

Strong

Leucovorin rescue is the standard of care after high-dose methotrexate in osteosarcoma, lymphoma, and acute lymphoblastic leukemia, with decades of clinical use and unambiguous evidence that it reduces methotrexate-induced myelosuppression, mucositis, and nephrotoxicity. It bypasses the DHFR blockade caused by methotrexate, restoring tetrahydrofolate pools in normal cells.

5-Fluorouracil potentiation in colorectal cancer

Strong

Adding leucovorin to 5-fluorouracil stabilizes the ternary complex between FdUMP and thymidylate synthase, increasing tumor cell kill. Multiple large randomized trials and meta-analyses have established this combination (and its FOLFOX/FOLFIRI derivatives) as a backbone of colorectal cancer chemotherapy, with improved response rates and survival versus 5-FU alone.

Megaloblastic anemia due to folate deficiency

Strong

Leucovorin corrects megaloblastic anemia caused by folate deficiency, including cases where DHFR is impaired (e.g., congenital deficiency, or after antifolate exposure). For uncomplicated nutritional folate deficiency, oral folic acid is preferred for cost and simplicity; leucovorin is reserved for situations where DHFR-independent folate is required.

Cerebral folate deficiency

Good

In cerebral folate deficiency syndromes - typically caused by folate receptor alpha autoantibodies or genetic transport defects - high-dose oral leucovorin can cross into the CNS and normalize CSF 5-methyltetrahydrofolate, with reported improvements in seizures, motor function, and developmental measures in case series and small open-label studies. Emerging interest in autism with folate receptor autoantibodies remains investigational.

How it works

Leucovorin contains a mixture of plant compounds, and the exact mechanism behind any effects depends on the specific preparation, the part of the plant used, and how it is extracted. Concentrations of active constituents can vary substantially between products. Most botanical effects are studied as a whole-plant or extract effect rather than tied to a single isolated molecule. Without strong human trial data, claims about how Leucovorin works should be treated cautiously.

Dosage

Prescription only - doses are set by a clinician and vary widely by indication. Methotrexate rescue typically uses 10-25 mg every 6 hours (oral, IM, or IV) starting 24 hours after methotrexate and continued until methotrexate levels fall below a threshold. Colorectal cancer regimens combine leucovorin with 5-fluorouracil at protocol-specific doses. Cerebral folate deficiency and inborn errors of folate metabolism use chronic oral dosing, often 0.5-5 mg/kg/day. Leucovorin should not be substituted for folic acid in routine supplementation without a specific clinical indication.

When and how to take it

There is no widely agreed best time to take Leucovorin. Many people take botanicals with food to reduce the chance of stomach upset. Follow the directions on the product label.

3 commercial forms

Whole herb powder

Contains the full spectrum of plant compounds; potency varies by source.

Dried, ground plant material in capsules or loose form.

Standardized extract

Concentrated and standardized to a marker compound for more consistent potency.

Often more concentrated than whole-herb powder and used in clinical research.

Liquid tincture

Alcohol or glycerin extraction; absorbed quickly when taken sublingually.

Easy to adjust dose by drops.

Safety

Leucovorin should never be co-administered intrathecally and is contraindicated in pernicious anemia or other vitamin B12 deficiency anemias , where it can produce hematologic improvement while neurologic damage progresses. It markedly potentiates the toxicity of 5-fluorouracil (more diarrhea, mucositis, myelosuppression) - an intended effect in oncology but a hazard if doses are mismatched. Leucovorin can reverse the antifolate effect of trimethoprim, pyrimethamine, and sulfonamides , reducing their efficacy against Pneumocystis , toxoplasmosis, and bacterial infections. Allergic reactions, including anaphylaxis, have been reported. Use only under medical supervision.

Who should be cautious

People who are pregnant or breastfeeding should generally avoid Leucovorin unless a healthcare provider has cleared it, because safety data in these groups is limited. Anyone with a chronic medical condition, scheduled surgery, or who takes prescription medications should consult a healthcare provider first.

Interactions

Possible interactions between Leucovorin and prescription medications have not been comprehensively studied. Botanicals can affect liver enzymes, blood clotting, blood pressure, or blood sugar in some cases. If you take prescription medications, check with a pharmacist before starting.

Frequently asked questions

What is Leucovorin used for?⌄

Leucovorin is used traditionally for various supportive purposes. Human evidence for specific health claims is generally limited, so it is best treated as a complementary option rather than a treatment.

Is Leucovorin safe?⌄

Leucovorin is generally well tolerated at typical doses, but quality varies between products. People who are pregnant, breastfeeding, taking prescription medications, or managing a medical condition should check with a healthcare provider first.

How long does it take to work?⌄

Effects of botanical supplements often take several weeks of consistent use, if they appear at all. Reassess after 8-12 weeks of regular use.

References

  • Leucovorin on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link
  • Research on Leucovorin (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.