Is a daily 1,000 mcg dosage of vitamin B12 safe?

Vitamin B12 is unlikely to be toxic, even in high daily dosages. As most people need only 2.4 mcg of vitamin B12 daily, taking a 1,000 mcg dosage of vitamin B12 once a week is enough for healthy people. Only people with severe vitamin B12 deficiency can have much higher doses of 5,000 mcg.

How much vitamin B12 should I take daily?

The recommended daily intake of vitamin B12 is only 2.4 mcg for most adults. Pregnant and lactating women need 2.6 mcg and 2.8 mcg of vitamin B12 a day, respectively.

Although the recommended daily dosage for vitamin B12 may not sound much, vitamin B12 deficiency is pretty common! Up to 15% of the population fail to consume enough vitamin B12.

That’s because common foods, such as dairy, milk, meat, chicken, fish, and eggs contain moderate amounts of vitamin B12, whereas plant-based foods are poor in vitamin B12.

Neither plant, nor animals produce vitamin B12. Only some soil bacteria synthesize it. When people used to drink water directly from lakes, wells, or streams, there wasn’t such thing as vitamin B12 deficiency!

Vitamin B12 deficiency & adverse effects

Vitamin B12 deficiency can cause anemia, neurological changes, constipation, loss of appetite, weight loss, hair loss, lack of balance, depression, confusion, dementia, and poor memory.

Moreover, vitamin B12 deficiency can cause fatigue, weakness, or soreness, as vitamin B12 is necessary for the formation of red blood cells and plays a key role in energy metabolism! Red blood cells are responsible for delivering oxygen to the body!

Furthermore, vitamin B12 is required for DNA synthesis, good neurological function, and normal homocysteine levels.[1]

Is a vitamin B12 dosage of 1,000 mcg safe?

Actually, there hasn’t been established a maximum safe dose for vitamin B12, as vitamin B12 has low toxicity. There are no adverse effects for excess vitamin B12 intake in healthy people. Neither from food nor supplements.

Furthermore, according to a study published in the New England Journal of Medicine, even a daily vitamin B12 intake of 1,000 mcg for 5 years didn’t cause any serious adverse effect.[2]

So, if you’re healthy, and you don’t take any drugs, taking 1,000 mcg of vitamin B12 daily is probably safe. However, extremely high amounts of vitamin B12 won’t help you further. Your body will excrete most of it.

Always consult your physician before taking any supplements or changing your diet.

You can take high amounts of vitamin B12 from supplements once a week

There is no need to take vitamin B12 supplements every day. You can take vitamin B12 once a week. As the biological half-life of vitamin B12 in the plasma is about 6 days, you could take 1,000 mcg of vitamin B12 once a week with the same health benefits.[3]

Most vitamin B12 supplements contain a 500 mcg, 1,000 mcg, or even 5,000 mcg dosage per capsule. If your doctor hasn’t advised you otherwise, taking a pill of 1,000 mcg once a week is probably more than enough.

Extremely high dosages of 5,000 mcg are too much for healthy people. Although supplements are unlikely to cause vitamin B12 overdose, only people with severe vitamin B12 deficiency due to health issues may benefit from such mega dosages.

You’ll find a wide variety of vitamin B12 supplements on iHerb.

Vitamin B12 dosage for seniors

There are people that can’t absorb vitamin B12 from food or even oral supplements. In most cases, these are seniors who have reduced levels of stomach acidity or intestinal disorders.

For instance, up to 30% of elderly people may have atrophic gastritis, a condition in which the stomach can’t secret enough hydrochloric acid, limiting the absorption of vitamin B12 from food or oral supplements.

However, vitamin B12 from supplements or even fortified foods is more absorbable. So, it’s recommended, people older than 50 years to take vitamin B12 supplements or eat foods fortified with vitamin B12! In most cases, a dose of 1,000 mcg of vitamin B12 once a week is enough.

Extremely high doses of vitamin B12 from injections

There are cases that people have severe vitamin B12 deficiency or can’t absorb vitamin B12 from oral supplements or food. Then, vitamin B12 injections may be the best solution. Vitamin B12 injections bypass potential barriers to the absorption of vitamin B12.[4]

Moreover, injections of high dosages of vitamin B12 are very safe. Even when vitamin B12 is administered intramuscularly up to 3,000 times the recommended dietary allowance, it hasn’t any toxic effect.[5]

Guidelines of vitamin B12 supplementation

What should your blood level of vitamin B12 be?

As a rule of thumb, vitamin B12 blood values below 170–250 pg/mL for adults indicate a vitamin B12 deficiency. Furthermore, homocysteine levels higher than 13 micromol/L or blood values of methylmalonic higher than 0.4 micromol/L might also suggest a vitamin B12 deficiency.[1]

How long does it take for vitamin B12 supplements to work?

Every person reacts differently to vitamin B12 supplementation. For instance, older persons may need vitamin B12 injections in order to increase their levels of vitamin B12. It takes about 72 hours for vitamin B12 injections to work.[6]

What is the best time to take vitamin B12?

As vitamin B12 is a water-soluble vitamin, it’s dissolved in water. The best time to take vitamin B12 supplements is in the morning before eating breakfast or before a meal, on an empty stomach.

Is it OK to take vitamin B12 at night?

The best time to take vitamin B12 is in the morning with an empty stomach. You better avoid taking vitamin B12 supplements at night, as high doses of vitamin B12 may affect sleep quality.[7]

Most noteworthy, you should eat foods high in melatonin in order to sleep better at night. Melatonin is known as the sleep hormone.