The fastest increase is typically achieved with appropriately dosed supplementation because absorption and dosing are more standardized. Diet can also help: dark leafy greens, legumes, citrus fruits, avocado, and folate-fortified foods contribute. That said, “speed” is not the only KPI—sustainable adequacy is the real target. Malabsorption, alcohol use, certain medications, or coexisting deficiencies (B12, iron) can slow improvement. A strong plan addresses both the source (diet/supplement) and the root cause (why levels are low).