The pattern is real, the effect is narrow. High homocysteine in older adults comes with 64% higher odds of hearing loss, and low folate raises the odds of mild loss too ¹. That association shows up across continents and age groups. But the one folic-acid trial moved speech-range hearing by only 0.7 dB over three years, too small to hear, and it ran in a country that doesn't fortify its food, so it barely transfers to anyone eating fortified cereal ².

For tinnitus, the split is sharp. B12 injections eased chronic ringing only in the people who were deficient to start; everyone else, and placebo, got nothing ³. B12 helps the people who need B12, and no one else.

This is for a few groups, not everyone. Deficiency is common enough to catch in adults over 60 (the stomach lining thins with age), long-term vegans, people on metformin for years ⁴, long-term acid-blocker users like omeprazole, and anyone with pernicious anemia or prior stomach surgery. Eat a normal mixed diet and sit in none of these? You can stop here.

Test before you treat. The whole thing turns on one blood draw.

If you're genuinely deficient, here's the arc. By week four the afternoon energy floor lifts. Around six weeks, any tingling in fingers and toes retreats, and tinnitus tied to deficiency starts easing on severity scores ³. Months three to six: brain fog and word-finding gaps settle. Hearing is the slowest and never fully restored; the payoff is a gentler slope, roughly 40% less speech-frequency decline over three years ². Across a decade, that's hearing aids at 78 instead of 72. Not deficient? The payoff is about zero.