If you are low in vitamin B12, a common recommended dose for oral supplements is about 1,000 mcg daily. But you should make sure to ask your healthcare provider about how much vitamin B12 you should look for in a supplement.
There is no risk of an overdose when taking large amounts of vitamin B-12 such as 1000 mcg, because it is a water-soluble vitamin. Meaning the body will use the amount that it needs then the excess will be excreted through urine.
For B12 deficiency, a typical injection dose is 1,000 mcg once a week for 4 to 8 weeks and then 1,000 mcg once a month. But dosages can vary depending on if you're treating severe, mild, or asymptomatic B12 deficiency.
The recommended daily amount for B12 is 2.4 mcg for adults. Pregnant and lactating women need higher amounts [1]. There is no upper intake limit for vitamin B12 because there is no known toxicity [2]. Most vitamin B12 supplements provide a range of strengths between 500 to 5,000 mcg [2].
In some people, high levels of B12 may cause gastrointestinal problems such as bloating and diarrhea. And if you have high blood pressure or poor cardiovascular health, having too much B12 may further complicate these issues. Pregnant and breastfeeding women may also need to be especially mindful of B12 levels.
It may take a few weeks before your vitamin B12 levels and symptoms (such as extreme tiredness or lack of energy) start to improve. If you have hydroxocobalamin injections to boost your vitamin B12 levels at the start of treatment, the cyanocobalamin tablets may start to work within a few days.
Once you begin treating your vitamin B12 deficiency, it can take up to six to 12 months to fully recover. It is also common to not experience any improvement during the first few months of treatment. If you can, it's a good idea to address what's causing the deficiency.
Around 50% to 98% of vitamin B12 is excreted from the body 48 hours after injection. Research shows that vitamin B12 has a half-life of 6 days in the blood, making it six days before the administered amount gets excreted from your body.
One large study found that women who took 1,000 mcg of vitamin B12, along with 2500 mcg of folic acid and 500 mg of vitamin B6 daily, reduced the risk of developing AMD, an eye disease that can cause loss of vision.
Ideal Vitamin B12 Dosage for Seniors
In some cases, high doses of 500 to 1000 micrograms per day might be necessary to reverse B12 deficiency.
“Take water-soluble vitamins on an empty stomach with a glass of water,” recommends Dr. Perez-Gallardo. And since it can be energizing, Dr. Perez-Gallardo says that the best time to take vitamin B12 is in the morning, so it won't affect your sleep.
Lifelong vitamin B12 supplements may be required at doses between 100 and 1,000 micrograms. As such, "B12 vitamin 1,000 mcg" refers to a high dose (1,000 micrograms) of vitamin B12 suitable for someone with nutrient absorption issues or pernicious anemia.
1000 mcg is about 400 times as much as 2.4 mcg.
Thus if you're otherwise healthy but still continue to feel tired after taking a B-12 supplement, it could be a sign of a mild allergic reaction. If a rash, difficulty breathing or swelling coincides with taking your dose of B-12, get to the doctor right away.
B12 injections may contribute to low potassium levels in your body. Though rare, this reaction can cause muscle cramping, extreme fatigue, and an irregular heartbeat.
Interactions between your drugs. No interactions were found between Vitamin B12 and Vitamin D3. However, this does not necessarily mean no interactions exist. Always consult your healthcare provider.
Low Blood Pressure
Deficiencies of vitamin B12 and folic acid can cause anemia, which can lead to low blood pressure, also known as hypotension. Vitamin B12 helps your body produce red blood cells so that adequate oxygen reaches each and every part of your body, including the heart.
Vitamin B12 deficiency can have distressing neuropsychiatric symptoms. It can have an etiological role in clinical presentations like depression, anxiety, psychosis, dementia, and delirium, requiring screening of at-risk populations.
A serum B12 above 300 pg/mL is interpreted as normal. Patients with B12 levels between 200 and 300 pg/mL are considered borderline, and further enzymatic testing may be helpful in diagnosis. Patients with B12 levels below 200 pg/mL are considered deficient.