B12, also known as cobalamin, is an essential vitamin that plays many crucial roles in the body. It is responsible for producing red blood cells, synthesizing DNA, and supporting the nervous system. Many people are deficient in B12, and this can lead to a variety of symptoms, including fatigue, weakness, constipation, loss of appetite, weight loss, depression, confusion, and more. The question is – can taking B12 supplements reverse these symptoms in someone who is deficient? Let’s take a closer look at the research and evidence around B12 and symptom reversal.
What causes B12 deficiency?
There are a few main causes of B12 deficiency:
- Pernicious anemia – this autoimmune disease hampers the body’s ability to absorb B12 from food. It is responsible for most clinical cases of deficiency.
- Gastrointestinal disorders – conditions affecting the stomach, intestines or pancreas can interfere with B12 absorption from food. This includes celiac disease and Crohn’s disease.
- Medications – some drugs such as proton pump inhibitors and metformin can deplete B12 levels over time.
- Inadequate intake – a long-term diet low in animal foods may lead to lower B12 intake and status.
- Other – factors like alcohol abuse, smoking, kidney disease, and age can also impair B12 absorption and cellular uptake.
When the body is unable to absorb enough B12 from food over a long period, stores become depleted and deficiency sets in. This means the body doesn’t have enough of the vitamin available to carry out its many crucial functions.
Common symptoms of B12 deficiency
Some of the most common symptoms associated with B12 deficiency include:
- Fatigue and weakness – B12 plays a key role in energy production and red blood cell formation. Without adequate B12, many people feel persistently tired and weak.
- Numbness and tingling – B12 supports the nervous system and some people experience numb, tingly sensations in the hands, feet, arms and legs with deficiency.
- Muscle cramps – Linked to the role B12 plays in nerves and energy production, muscle cramping is a common symptom.
- Dizziness – B12 deficiency can lead to dizziness and trouble with balance.
- Pale skin – With a lack of B12, the body can’t produce enough healthy red blood cells. Skin may appear pale or yellowish.
- Mental health issues – Depression, anxiety, paranoia and memory problems have been associated with B12 deficiency.
- Vision changes – Blurry or double vision can occur as optic nerves are affected.
- Glossitis – The tongue may appear swollen, inflamed and red due to B12 deficiency.
Left untreated over many years, B12 deficiency can potentially lead to permanent nerve damage. That’s why it’s so important to catch it early and correct levels.
How is B12 deficiency diagnosed?
If symptoms of B12 deficiency are present, a doctor will typically check blood levels of the vitamin. A B12 blood test measures levels of both active and inactive forms in the body.
Results indicating deficiency are:
- Serum B12 levels below 200 pg/mL
- Serum homocysteine levels above 15 nmol/L
- Serum methylmalonic acid (MMA) levels above 0.4 μmol/L
Doctors may also examine red blood cells through a peripheral blood smear to look for macrocytic anemia, which can indicate B12 deficiency. Bone marrow testing can help confirm diagnosis as well.
What is the recommended daily intake of B12?
The recommended daily intake of B12 is:
- Infants up to 6 months – 0.4 mcg/day
- Babies 7-12 months – 0.5 mcg/day
- Children 1-3 years – 0.9 mcg/day
- Children 4-8 years – 1.2 mcg/day
- Children 9-13 years – 1.8 mcg/day
- Teens 14-18 years – 2.4 mcg/day
- Adults – 2.4 mcg/day
- Pregnant women – 2.6 mcg/day
- Breastfeeding women – 2.8 mcg/day
These recommendations are based on the amount needed to maintain healthy blood levels of B12. However, many experts suggest older adults should get extra B12 from supplements or fortified foods due to reduced absorption capabilities.
What foods contain B12?
While small amounts of B12 are found in some plant foods, the highest dietary sources of B12 all come from animal products:
- Beef liver – 1 oz contains >1000% DV B12
- Clams – 84g contains ~1000% DV B12
- Fortified cereals – contain ~25-100% DV B12 per serving
- Trout – half fillet contains ~50% DV B12
- Salmon – half fillet contains ~50% DV B12
- Tuna – 3oz contains ~40% DV B12
- Eggs – large egg contains ~10% DV B12
- Milk – 1 cup contains ~20% DV B12
- Yogurt – 6oz contains ~15-25% DV B12
- Beef – 3oz contains ~15-20% DV B12
For those following plant-based diets, foods fortified with B12 like nutritional yeast and some plant milks can help meet needs. But supplements are often required for strict vegans to prevent deficiency.
What are the best B12 supplements?
There are a few main types of B12 supplements available:
- Cyanocobalamin – the most common and readily available form. Considered stable and effective.
- Methylcobalamin – thought to have higher bioavailability. May be preferable for those with absorption issues.
- Hydroxocobalamin – can be administered via injection for therapeutic purposes.
- Adenosylcobalamin – a naturally occurring form in the body that may offer higher bioactivity.
The various forms are generally considered equally effective at correcting deficiency when taken at appropriate doses. Cyanocobalamin is typically the most affordable option. Time release or sublingual tablets and lozenges can help increase absorption.
The recommended supplemental dose for adults is 1000-2000 mcg per day of B12 or a weekly dose of 2000 mcg. Higher therapeutic doses may be used to treat deficiency. B12 is considered safe even at high levels.
B12 supplements are widely available as tablets, capsules, sublingual liquids, nasal gels, injections and prescription formulations. Multivitamins also provide B12. Speak to your doctor to determine the best B12 supplement and dosage for your needs.
Can B12 injections help reverse deficiency?
For those with very low B12 levels or pernicious anemia, B12 injections may be used initially to rapidly correct deficiency. They allow high levels of vitamin to directly enter the bloodstream, bypassing any absorption issues in the gut.
When administered properly, B12 injections can quickly restore blood levels and provide symptomatic relief. Some doctors will administer a set of weekly injections, then monthly shots to keep levels adequate. Ongoing injections may be necessary for certain patients.
Compared to oral supplements, B12 injections are considered very effective for boosting blood levels into a healthy range, especially when deficiency is severe. However, regular oral B12 can also eventually correct deficiency in many cases.
How long does it take to reverse B12 deficiency?
Most people deficient in B12 will start to feel better within weeks of receiving supplementation, whether via injections or high-dose oral B12 supplements.
However, it can take up to 6 months or more of continued supplementation for B12 levels to fully normalize in those who were severely deficient. For this reason, ongoing B12 supplementation is important after finishing an initial treatment regimen.
Symptoms related to nerve damage, such as numbness in the hands and feet, are likely to improve with B12 therapy but may persist if deficiency was prolonged. B12 helps halt progression but cannot fully reverse nerve damage once it has occurred. The earlier treatment is started, the better the outcomes tend to be.
With proper B12 supplementation tailored to the individual, most symptoms of deficiency can at least partially reverse. But every person is unique in how quickly their levels respond and symptoms improve. Working closely with a doctor helps ensure optimal B12 restoration.
What are the side effects of too much B12?
B12 is considered very safe, even at high supplemental doses. No UL (upper tolerable limit) has been set for B12 intake.
Because it is a water-soluble vitamin, excess amounts are generally excreted in urine rather than building up to toxic levels in the body.
Very rare side effects associated with excessive B12 supplementation may include:
- Itching, rash or swelling with injections
- Rapid heartbeat or breathing
- Anxiety
- Diarrhea
- Blood clots
Unless an allergy is present, these effects are unlikely even with very high B12 doses. Always start supplements at normal recommended amounts and only increase under medical supervision.
For most people, there is minimal cause for concern with generous B12 supplementation to correct deficiency. Monitoring symptom improvements and eventual blood retesting helps confirm you are taking the right amount.
Can you reverse B12 deficiency without supplements?
It is difficult to reverse B12 deficiency without some supplemental intake, since sources from most foods are inadequate to restore depleted body stores quickly.
Relying solely on high-B12 foods would require consuming significant amounts of beef, liver, clams, trout, fortified cereals and other rich sources daily over a long period. For vegans and vegetarians, this would likely be unrealistic.
Building meals around eggs, dairy, seafood and meat can help regain some B12 stores without supplements. But tablets, capsules, liquids or injections will typically be needed, at least initially, to restore optimal B12 status if deficiency is present.
Ongoing supplementation may not always be required after levels normalize, if dietary intake can be improved. But since B12 absorption capacity decreases with age and other factors, a regular supplement or fortified foods often become necessary.
Consult your doctor to determine the best sources and dosages of supplemental B12 to reverse your deficiency symptoms and meet needs long-term. With the right treatment plan, reversing B12 deficiency is very possible.
Can B12 deficiency symptoms return?
If B12 deficiency was caused by an underlying absorption problem or autoimmune disorder, symptoms are likely to return when supplementation is stopped, since the body cannot obtain enough from food alone.
For instance, those with pernicious anemia or celiac disease may need lifelong B12 supplements or injections to manage symptoms, even if their levels test normal. Otherwise, deficiencies will reoccur.
Likewise, older adults over 50 may see symptoms come back due to declining ability to absorb B12 from foods. With lower intakes from animal sources, supplements often become necessary with age.
Symptoms may also return if B12 supplementation is not maintained after treatment, since body stores drain over time. Ongoing intake through diet or supplements helps prevent recurrence of symptoms in those predisposed to deficiency.
Working with your doctor can help determine the long-term supplementation needs to keep your B12 levels in the optimal range and symptoms reversed. Regular blood testing and monitoring of symptoms allows for adjusting intake as necessary over time.
The bottom line
B12 deficiency can often be reversed with adequate supplementation tailored to the individual. Oral supplements, injections or dietary improvements help restore blood levels and provide symptom relief in most cases.
However, those with absorption disorders may need ongoing high-dose supplementation or B12 shots to prevent recurrence of symptoms. Close monitoring and follow-up with a doctor helps ensure treatment is effective long-term.
While nerves damaged by prolonged deficiency may not fully recover, most symptoms can improve significantly or resolve with prompt, appropriate B12 therapy. Overall the outlook is very good when deficiency is caught early and corrected.
