Vitamin B12 can start improving energy within days via injections, but for oral supplements, it often takes a few weeks to months to notice significant energy boosts, depending on the severity of your deficiency and absorption. Injections bypass the digestive system, leading to faster results (24-72 hours), while oral tablets require consistent intake to build up levels, with full effects taking longer, especially for severe cases or neurological improvements.
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.
Some B12 supplements promise an instant energy boost. But that's often because they're packed with artificial stimulants. B12 isn't producing these on-demand results.
The RDA for females who are pregnant is 2.6 mcg of vitamin B12 a day. Most people get enough vitamin B12 from their diet. When adding up how much vitamin B12 you are getting, remember to count amounts from foods, drinks, and from any supplements you are taking.
What is vitamin B12 and what does it do? Vitamin B12 is a nutrient that helps keep your body's blood and nerve cells healthy and helps make DNA, the genetic material in all of your cells. Vitamin B12 also helps prevent megaloblastic anemia, a blood condition that makes people tired and weak.
5 Symptoms That Indicate High Vitamin B12 Levels
People may experience frequent episodes of dizziness with no apparent cause. Headaches may be persistent and more intense than common tension headaches.
In fact, some studies have even suggested the opposite. For instance, one study noted that individuals who regularly took vitamin B12 supplements gained between 2.5 to 17 fewer pounds (1.2 to 7.7 kg) over a decade than those who didn't supplement.
Symptoms of vitamin B12 or folate deficiency
The foods highest in Vitamin B12 are animal products, with clams and liver (beef, lamb) being exceptionally rich sources, often providing several hundred percent of the daily value in a single serving, alongside seafood like mussels, sardines, and salmon, dairy, eggs, and fortified cereals and nutritional yeast for vegans.
Individuals experiencing a deficiency often report feeling unusually tired or weak, even after adequate sleep. This symptom arises because a lack of B12 impairs the production of red blood cells, leading to fewer cells to transport oxygen throughout the body.
While most people feel some benefits within 24 hours, your individual experience may vary based on: Your current B12 levels — If you're deficient, the effects will be more noticeable and immediate. Your body's absorption rate — Some individuals naturally metabolize B12 faster than others.
Which vitamins and minerals can help with tiredness and fatigue?
People with very low vitamin B-12 levels can have symptoms such as fatigue, muscle weakness, stomach problems, nerve damage, vision problems and mood changes. They also may have low iron, called anemia, or low blood counts. The recommended daily amount of vitamin B-12 for adults is 2.4 micrograms (mcg).
B12 is a key nutrient for nervous system health. It is important for producing serotonin and dopamine, which are mood-enhancing neurotransmitters. As a result, vitamin B12 can help to prevent and treat depression and anxiety. It can improve focus and memory as well.
Lack of vitamin B12 in your diet: People who don't eat enough foods that have vitamin B12 or don't eat foods fortified with B12 can develop a deficiency. Gastritis: Gastritis is inflammation of the stomach lining, and it's a common cause of vitamin B12 deficiency.
B12 deficiency can trigger specific food cravings, most notably for meat, fish, or eggs, as the body seeks animal-based sources to replenish the vitamin, especially in those on vegetarian/vegan diets or older adults. While cravings for sugary or salty foods can also signal general B-vitamin issues, the distinct urge for protein-rich animal products is a key indicator, but professional testing is crucial for confirmation.
Cutaneous manifestations associated with vitamin B12 deficiency are skin hyperpigmentation, vitiligo, angular stomatitis, and hair changes. A diagnosis of vitamin B12 deficiency is often overlooked in its early stages because these signs are not specific to vitamin B12 deficiency alone.
The Boots Vitamin B12 Blood Test Kit checks your vitamin B12 levels, using a finger-prick blood sample. Use of this kit requires internet access. All personal data in relation to this product, services and online platforms are collected and processed by MyHealthChecked.
While vitamin B12 is generally safe, taking excessively high doses, especially via injections, can cause side effects like headaches, nausea, diarrhea, dizziness, and skin rashes; rare serious issues include allergic reactions (anaphylaxis), increased heart rate, blood clots, and potential links to increased cancer risk or early death, requiring medical attention if severe symptoms appear.
Strengthens Hair Follicles to Promote Growth
This vitamin supports the production of keratin, the protein that makes up hair strands, helping them grow thicker and more resilient. When your body lacks B12, hair follicles may become weaker, leading to slower growth and thinning hair.
The worst symptoms of B12 deficiency involve severe neurological damage, including severe memory loss, confusion, dementia, psychosis, hallucinations, balance problems, trouble walking, and irreversible nerve damage (neuropathy), alongside serious mental health issues like severe depression or irritability, with physical signs including extreme fatigue, pale skin, and a sore, smooth tongue. These severe cognitive and neurological issues are the most concerning because they can become permanent if left untreated.
In conclusion, our results show that lower vitamin B12 was associated with insomnia symptoms and sleepiness in specific groups of participants. However, further research with objective measurements of sleep is crucial to assess the relationship between sleep and vitamin B12.
The best form of B12 is often considered methylcobalamin, as it's a naturally occurring, active form the body uses immediately, though adenosylcobalamin is also an active form, with a combination often recommended for better results, especially for deficiency or absorption issues, while cyanocobalamin, a cheaper synthetic option, is effective but requires conversion and is less ideal for some. For general supplementation, natural forms like methylcobalamin or adenosylcobalamin are preferred for better retention.
If you have vitamin B12–deficiency anemia, you may have the typical symptoms of anemia at first, such as fatigue, paleness, shortness of breath, headaches, or dizziness. If left untreated, you may start to notice brain and nervous system symptoms.