B12 deficiency can sneak up on you. You’re feeling strong and energetic, thinking clearly, feeling upbeat, and then gradually, maybe over the course of several months or even years, you begin to notice that you’ve lost the pep in your step.

Your mind and memory aren’t as sharp as they once were. Even mildly strenuous physical activity leaves you breathing hard, and instead of feeling pumped up after exercise, you feel exhausted.

What happened?

B12 Deficiency Graphic

Without a thorough workup, complete with analysis of targeted lab tests, you’ll never know what’s causing you to feel rundown. It could be stress, a lack of (or too much) exercise, a buildup of environmental toxins, or an undiagnosed infection. Or it might be any number of nutritional deficiencies, a combination of those deficiencies, or countless other possible contributing factors.

That’s why I always recommend consulting with a healthcare professional who is attached to a functional medicine practice and obtaining a complete workup and personalized plan of care before starting any treatment, or even taking an over-the-counter supplement. Until you test, you don’t know the root cause of what’s ailing you or what your body may be lacking.

A complete workup often reveals numerous contributing factors and root causes, and one common factor is a vitamin B12 deficiency. Unfortunately, diagnosing and treating B12 deficiency and its underlying cause(s) is more complicated than just ordering a blood test and taking a B12 supplement. In this post, I explain why. But first, it’s important to recognize the symptoms and possible causes of B12 deficiency.

Symptoms of Vitamin B12 Deficiency

Vitamin B12 plays an important role in physiological processes that affect different systems in the body. As a result, symptoms of B12 deficiency can vary considerably, both in symptom type and severity. Here are some common symptoms associated with B12 deficiency:

  • Fatigue and weakness: Feeling unusually tired and weak is one of the most common symptoms of B12 deficiency. This is because B12 is essential for the production of red blood cells, which carry oxygen throughout the body.
  • Anemia: B12 deficiency can lead to a type of anemia called megaloblastic anemia. In this condition, red blood cells are larger and fewer in number, which can result in reduced oxygen-carrying capacity and lead to fatigue, pale skin, and shortness of breath.
  • Nervous system dysfunction: B12 plays a crucial role in maintaining the health of the nervous system. Deficiency can lead to symptoms such as numbness, tingling, or a “pins and needles” sensation in the hands and feet. It can also cause difficulty walking, balance problems, and even affect cognitive functions including memory and concentration.
  • Neuropsychiatric symptoms: B12 deficiency has been associated with mood changes, including depression, anxiety, and irritability. Some individuals may experience more severe neurological symptoms like confusion, memory loss, and even hallucinations in severe cases.
  • Digestive problems: B12 deficiency can lead to digestive issues, such as loss of appetite, weight loss, and constipation.
  • Glossitis and mouth ulcers: Deficiency of B12 can cause inflammation of the tongue (glossitis) and mouth ulcers.
  • Yellowing of the skin: In severe cases, B12 deficiency can affect the liver’s ability to process bilirubin, leading to jaundice and yellowing of the skin and eyes.
  • Heart palpitations and shortness of breath: B12 deficiency can impact the cardiovascular system, leading to palpitations and a rapid heartbeat. Shortness of breath can also occur due to the reduced oxygen-carrying capacity of the blood.
  • Vision changes: Some individuals with B12 deficiency may experience blurred vision or changes in vision.

Recognizing the Causes of B12 Deficiency

Treating vitamin B12 deficiency requires more than just supplementing with B12. I always recommend that you first need to identify and address the root cause of the deficiency. In addition, knowing what’s causing it can help you make better informed decisions about the B12 supplement that’s likely to be most effective. Vitamin B12 deficiency can manifest in several different types, each with distinct causes and characteristics:

  • Dietary deficiency occurs when an individual does not consume enough foods containing vitamin B12, which is primarily found in animal products such as meat, fish, dairy, and eggs. Vegans and vegetarians are particularly at risk if they do not adequately supplement their diet with B12 sources.
  • Dietary factors, such as a diet high in nitrites (commonly found in processed foods) or excessive alcohol intake, can contribute to B12 deficiency. Alcohol severely depletes B vitamins over time. Reducing alcohol consumption and eating more vegetables and fruits are good ways to start repairing your liver and GI tract.
  • Pernicious anemia is an autoimmune condition. The body’s immune system attacks the cells in the stomach lining responsible for producing a protein called intrinsic factor, which is necessary for the absorption of vitamin B12 in the small intestine. Without intrinsic factor, B12 cannot be absorbed effectively, leading to deficiency. Pernicious anemia is often treated with B12 injections. A blood test can reveal whether your body is producing antibodies against parietal cells or intrinsic factor. If the antibodies are present at elevated levels, you have pernicious anemia.
  • Atrophic gastritis involves inflammation and thinning of the stomach lining, which can impair the production of intrinsic factor and hinder B12 absorption. This condition is more common in older adults.
  • Malabsorption disorders can develop from certain gastrointestinal disorders, such as celiac disease, Crohn’s disease, and bacterial overgrowth in the small intestine. These disorders can interfere with the absorption of B12, even if sufficient intrinsic factor is present. When the intestines or stomach lining is weakened due to chronic inflammation, B12 absorption can be impacted. It’s often common to find malabsorption of B12 associated with hypothyroidism and Hashimoto’s thyroiditis. Among my patients with hypothyroid (low thyroid), if they show signs of fatigue and weight gain, I test them for intrinsic factor antibodies and B12 anemia.
  • Medications may impair absorption of vitamin B12. For example, long-term use of proton pump inhibitors (PPIs) or metformin can affect B12 absorption by altering stomach acidity or interfering with normal absorption processes. Too many patients are being kept on PPIs way longer than they should be. These medications are meant for short-term use of up to three months. Taking an acid-blocking medication for several years can significantly diminish a person’s absorption of vitamin B12, leading to symptoms of fatigue, neuropathies, and weakened immunity. I work closely with my patients who are on acid-blocking medication to find the source of the issue, which is often related to diet and lifestyle or mast cell activation from exposure to medications, toxins, or infection. Birth control medications — Yasmin, Loestrin, Yaz, and other birth control pills; intrauterine devices (IUDs); and injections — can also deplete B12.
  • Surgical procedures involving the stomach or intestines, such as gastric bypass surgery, can lead to reduced B12 absorption due to alterations in the digestive tract’s anatomy. If you’ve had abdominal surgery or gastric bypass and you have symptoms of B12 deficiency, B12 injections may help.

Checking B12 levels in the blood does not provide adequate information and insight into whether you have a vitamin B12 deficiency.

Research has shown that false negatives are common when looking at B12 levels alone in blood tests. You may have normal or even high levels of B12 on your blood tests and still suffer from B12 anemia because the vitamin isn’t being absorbed into your red blood cells. I have witnessed this many times in my practice, and it’s usually, but not always, associated with hypothyroid, celiac disease, and elevated levels of intrinsic factor antibodies. In these cases, starting B12 injections to see if symptoms resolve is an important first step.

Choosing the Right Form of B12 Supplementation

Not all forms of vitamin B12 are the same. When you’re shopping for a B12 supplement, pay attention not only to the milligrams and recommended daily allowance (RDA), but also to the chemical composition:

  • Methylcobalamin is one of the active forms of vitamin B12. It plays a crucial role in various biochemical reactions in the body, including the methylation cycle, which is important for DNA synthesis, nervous system function, and the conversion of homocysteine to methionine (elevated homocysteine increases your risks for dementia, heart disease, and stroke). Methylcobalamin is used as a supplement to address B12 deficiency and support nerve health.
  • Adenosylcobalamin is another active form of vitamin B12. It is involved in energy production processes, particularly in the mitochondria, where it helps convert methylmalonyl-CoA to succinyl-CoA. This reaction is essential for the breakdown of certain amino acids and fatty acids. Adenosylcobalamin is also important for maintaining healthy nerve function.
  • Cyanocobalamin is a synthetic form of B12 that is often used in supplements and fortified foods. It is converted into the active forms of B12 (methylcobalamin and adenosylcobalamin) once it is in the body. Since many of my patients have MTHFR mutations (gene mutations that make it more difficult for the body to convert cyanocobalamin into an active form of B12), I prefer to avoid this type of B12 supplementation.
  • Hydroxocobalamin is a natural form of B12 sometimes used in medical treatments, particularly for B12 injections. It has a longer duration of action in the body compared to other forms and is often chosen when a sustained release of B12 is desired. Hydroxocobalamin can also be converted into the active forms of B12 as needed.

For many people, hydroxocobalamin is the best form of vitamin B12. Here’s why:

  • Sustained release: Hydroxocobalamin has a longer duration of action in the body compared to other forms of B12, such as cyanocobalamin. This sustained-release property can be beneficial for individuals who require less frequent injections or treatments.
  • Nitric oxide scavenging: Hydroxocobalamin can also act as a scavenger for nitric oxide, a molecule that plays a role in regulating blood vessel dilation and blood pressure. This property can be useful in certain medical conditions, such as septic shock, where high levels of nitric oxide contribute to blood vessel dilation and decreased blood pressure.
  • Treatment of certain inherited disorders: Some inherited metabolic disorders, such as methylmalonic acidemia and homocystinuria, may benefit from hydroxocobalamin treatment due to its role in converting methylmalonyl-CoA to succinyl-CoA and facilitating the conversion of homocysteine to methionine. While many people don’t have a complete inability to process B12, about 20 percent of the population has some form of MTHFR mutation that can impact B12 metabolism. In these cases, I prefer hydroxocobalamin.
  • Individual patient response: In some cases, patients may respond better to hydroxocobalamin than other forms of B12. This can be due to variations in individual metabolism and absorption.

The Doctor Says: While hydroxocobalamin has distinct advantages in certain contexts, other forms of B12 — such as methylcobalamin and cyanocobalamin — also have their own uses and benefits. The choice of B12 form should be made based on individual patient needs.

Are B12 Injections Right for You?

The best way to supplement is with injections. Injections can be done at home or in your doctor’s office, intramuscularly or subcutaneously. Liquid formulations taken orally are also absorbed well, but I don’t recommend them for patients who test positive for parietal cell antibodies or those with severe B12 deficiencies. When you start receiving B12 injections, you can expect your symptoms to start to improve within a few short weeks. Depending on your condition, you may require lifetime B12 injections on a weekly or monthly basis.

If you suspect you have a B12 deficiency, consult a healthcare professional for diagnosis and appropriate treatment. Treatment often involves B12 supplementation, either through oral supplements or injections, depending on the severity and underlying cause of the deficiency.

I like to supplement with a variety of B vitamins, not just B12, because B12 uses other vitamins when it becomes active in the body. For example, to make red blood cells, you need B12 and B9 (folate). Taking a B12 supplement without additional folate can cause a folate deficiency. There are other B vitamins that are needed include B1, B2, B3 (niacin), B5, and B6. These may be administered through an IV or oral supplement depending on the individual and their plan of care.

If you think you may be suffering with a B12 deficiency, take the next step and contact me to schedule your initial consultation. I will work closely with you to identify the root cause of what’s ailing you and develop a personalized plan of care that will put you back on the road to restoring and optimizing your health and fitness.

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About the Author: Dr. Matt Lewis, D.C., DACBN, CFMP®, specializes in diagnosing and treating the underlying causes of the symptoms related to chronic and unexplained illness through nutrition, lifestyle, chiropractic, and other natural approaches to whole-health healing in Tampa, Fla. Dr. Lewis has 20 years of experience practicing nutritional and holistic medicine. He earned his B.S. in Biology from Shenandoah University, his Doctorate in Chiropractic from Life University, his Diplomate status in Clinical Nutrition from the American Clinical Board of Nutrition, his CFMP from Functional Medicine University, and his certification as a Digestive Health Specialist (DHS) through the Food Enzyme Institute. Dr. Lewis’ passion for health and wellness stems from his own personal experience. With a family history of autoimmune conditions and diabetes, and his own lab tests showing his genetic susceptibility to Hashimoto’s thyroiditis (autoimmune thyroid), Dr. Lewis has learned how to restore his own health and vigor to prevent the onset of these and other illnesses and live an incredibly active life. Through this process, he acquired a deeper understanding of health and wellness, which he now offers his patients in Tampa and elsewhere.