Most adults need 1.3 mg of vitamin B6 and 2.4 mcg of vitamin B12 per day. Those numbers cover the majority of healthy people between 19 and 50, but your age, diet, and medications can shift the target meaningfully in either direction. Here’s what the recommendations actually look like across different life stages and situations, and how much you can safely take as a supplement.
Daily B6 Requirements by Age
Vitamin B6 needs stay relatively flat through most of adulthood, then tick upward after 50. For both men and women aged 19 to 50, the recommended dietary allowance is 1.3 mg per day. After 50, men need 1.7 mg and women need 1.5 mg. Children require less: 0.5 mg for toddlers (ages 1 to 3), 0.6 mg for kids 4 to 8, and 1.0 mg for those 9 to 13. Teenagers need 1.2 to 1.3 mg depending on sex.
Pregnancy and breastfeeding raise the requirement. Pregnant women need 1.9 mg daily, and lactating women need 2.0 mg. B6 is actually used as a first-line treatment for pregnancy-related nausea, often at doses of 25 to 75 mg per day for short periods, well above the standard RDA but under medical guidance.
Daily B12 Requirements by Age
The B12 target for adults is 2.4 mcg (micrograms) per day. That number holds steady from age 14 onward. Pregnant women need 2.6 mcg, and breastfeeding women need 2.8 mcg. Children’s needs range from 0.9 mcg (ages 1 to 3) up to 1.8 mcg (ages 9 to 13).
The 2.4 mcg figure assumes you’re absorbing B12 normally from food. In practice, your body can only take in about 1.5 to 2.5 mcg of B12 per meal from dietary sources. That’s why the actual supplement doses you’ll see on store shelves are dramatically higher than the RDA.
Why Supplement Doses Are So Much Higher
If you’ve looked at B12 supplements, you’ve probably noticed they come in doses like 500, 1,000, or even 5,000 mcg, far beyond the 2.4 mcg RDA. This isn’t marketing excess. It reflects how poorly B12 is absorbed in supplement form. Your body absorbs roughly 5% of a 25 mcg dose and only about 1% of a 1,000 mcg dose. The higher the dose, the smaller the fraction that actually makes it into your bloodstream. So a 1,000 mcg tablet delivers roughly 10 mcg of usable B12, still plenty to meet your daily needs.
For people on a plant-based diet who get little or no B12 from food, common preventive recommendations include taking 50 to 100 mcg daily, or 2,000 mcg once a week (either as a single dose or split into two 1,000 mcg doses). Any of these approaches provides enough to prevent deficiency.
The Safety Gap Between B6 and B12
This is where the two vitamins diverge sharply. B12 has no established upper limit. The body doesn’t store excess amounts, and even large doses are generally considered safe. No tolerable upper intake level has been set because the risk of toxicity is extremely low. That said, chronically elevated B12 blood levels have been loosely linked to a higher risk of certain cancers and hip fractures, so taking megadoses without a reason isn’t a free pass.
B6 is a different story. The tolerable upper intake level for adults is 100 mg per day. Go above that consistently and you risk peripheral neuropathy, a type of nerve damage that causes numbness, tingling, and pain in the hands and feet. The irony is that B6 deficiency causes similar symptoms, so people sometimes take more B6 thinking they’re fixing the problem when they’re actually making it worse. Most adults eating a varied diet easily hit 1.3 mg from food alone, so high-dose B6 supplements are rarely necessary outside of specific medical situations.
Who Needs More Than the Standard Amount
Adults Over 50
As you age, the stomach produces less acid and fewer digestive enzymes. This makes it harder to extract B12 from the protein-bound form found in meat, fish, poultry, and dairy. Adults over 50 are advised to get their B12 from fortified foods or supplements, which contain a crystalline form that doesn’t require stomach acid for absorption. A clinical trial found that 500 mcg per day of this form was needed to reverse early signs of B12 deficiency in older adults, well above the 2.4 mcg RDA but consistent with the absorption math described above.
People Taking Metformin
Metformin, one of the most commonly prescribed medications for type 2 diabetes, interferes with B12 absorption in the gut. Evidence over the past two decades consistently shows higher rates of B12 deficiency among long-term metformin users. If you take metformin, periodic blood checks for B12 status are worth discussing, and supplementation may be appropriate.
Vegans and Vegetarians
B12 is found almost exclusively in animal products. Vegans who don’t supplement will eventually become deficient, often within a few years as the body’s stores deplete. A daily dose of 50 to 100 mcg, or a weekly dose of 2,000 mcg, is enough to prevent this. B6, by contrast, is widely available in plant foods like chickpeas, potatoes, bananas, and fortified cereals, so deficiency is uncommon on a plant-based diet.
Pills, Sublingual Tablets, or Injections
B12 comes in several forms: standard oral tablets, sublingual (under-the-tongue) tablets, and intramuscular injections. A large meta-analysis found that all three routes produced statistically comparable improvements in blood B12 levels. Intramuscular injections showed the highest average increase (about 307%), followed by oral supplements (285%) and sublingual (199%), but the differences were not statistically significant. For most people, a regular oral tablet works fine.
Injections are typically reserved for people with severe deficiency or absorption disorders that prevent the gut from taking in B12 at all. If you can absorb nutrients normally, there’s no proven advantage to choosing sublingual over a standard pill.
Quick Reference: Daily Targets
- B6, adults 19–50: 1.3 mg
- B6, men 51+: 1.7 mg
- B6, women 51+: 1.5 mg
- B6, pregnancy: 1.9 mg
- B6 upper limit: 100 mg (do not exceed long-term)
- B12, adults: 2.4 mcg from food; 50–100 mcg if supplementing
- B12, pregnancy: 2.6 mcg
- B12, adults 50+: up to 500 mcg from supplements or fortified foods
- B12, vegans: 50–100 mcg daily or 2,000 mcg weekly
- B12 upper limit: none established