Updated: Oct 25, 2021
Do B12 Shots for Weight Loss Really Work?
Published: Sep 7, 2020

Many have debated whether or not B12 shots for weight loss are effective for those looking to shed stubborn weight. Some doctors argue that B12 shots for weight loss are only effective in dropping pounds if you are deficient in vitamin B12. Others contest that B12 can have positive effects on a person’s weight loss regardless of a deficiency.

Weight loss clinics around the country offer B12 shots for weight loss as a part of their various programs. B12 shots are purported to increase your energy, boost your mood, heighten your metabolism, and improve sleep cycles. Celebrities like Rita Ora, Justin Timberlake, and Katy Perry swear by their benefits. B12 shots for weight loss and overall quality of life improvement are quickly becoming common practice for those interested in health and fitness – but do they work?

To better understand whether B12 shots result in weight loss, it is important to know what vitamin B12 is, what it does in the body, and what happens if you aren’t consuming or absorbing enough.

Vitamin B12 – What It is, and Where to Get It

Vitamin B12 is a water-soluble vitamin that is naturally present in animal-based food products, fortified processed foods, or dietary supplements or prescribed medication. Vitamin B12, also known as cobalamin, is involved in the metabolism of all cells within the human body. As one of eight B vitamins, it is an integral part of DNA synthesis and in fatty acid and amino acid metabolism. What does this mean? It means that without the proper consumption and absorption of vitamin B12, the human body cannot properly metabolize fats and carbohydrates.

In addition to its metabolic function, vitamin B12 is responsible for aiding the normal function of the nervous system through its position in the development of red blood cells in the bone marrow. Those with low levels of vitamin B12 can sometimes suffer from anemia and negative symptoms caused by an improperly functioning nervous system.

Vitamin B12 is the largest and most structurally complex vitamin in the human body, consisting of four almost identical forms: cyanocobalamin, hydroxocobalamin, adenosylcobalamin, and methylcobalamin. The forms commonly used in B12 shots for weight loss are cyanocobalamin and methylcobalamin.

Since your body does not naturally make B12, humans have to source this essential vitamin from food sources or daily, weekly, or monthly supplements. Food sources containing vitamin B12 include fish, meat, eggs, milk, cheese, and other dairy products. Those who do not consume animal products, such as vegans or vegetarians, need to get their vitamin B12 supply from other sources such as fortified cereals and vitamin supplements. The recommended daily intake (RDI) differs depending on age, diet, and other medical factors. Generally, the RDI for healthy adults over the age of 14 is between 2.4 mcg and 2.8 mcg. More specifically, here are the average recommended amounts by age:

  • Infants up to age 6 months: 0.4 mcg
  • Babies age 7-12 months: 0.5 mcg
  • Children age 1-3 years: 0.9 mcg
  • Kids age 4-8 years: 1.2 mcg
  • Children age 9-13 years: 1.8 mcg
  • Teens age 14-18: 2.4 mcg (2.6 mcg per day if pregnant and 2.8 mcg per day if breastfeeding)
  • Adults: 2.4 mcg (2.6 mcg per day if pregnant and 2.8 mcg per day if breastfeeding) (NIH, n.d.)

The following groups are at an elevated risk of developing a vitamin B12 deficiency and should closely monitor their levels:

  • Vegetarians and vegans
  • Adults over the age of 50
  • Gastrointestinal disorders like Crohn’s disease and celiac disease
  • Those who have had weight loss surgery, bowel resection, or surgery on another part of the digestive tract
  • Those who take metformin and acid-reducing medications
  • Those with specific genetic mutations, such as MTHFR, MTRR, and CBS
  • Those who regularly consume alcoholic beverages (NIH, n.d.)

What Happens When You’re Deficient in Vitamin B12?

B12 shots for weight loss are popular among those trying to manage their weight and body composition, but a vitamin B12 deficiency can cause many more serious problems than poor weight management. Because vitamin B12 is such an integral component of a properly functioning body, a B12 deficiency can affect the central nervous system, the cardiopulmonary systems, and your mental health.

One of the most serious conditions caused by vitamin V12 deficiency is Pernicious anemia, a condition in which the body is not producing enough red blood cells and can cause permanent damage to the nerves and organs if it goes untreated. This form of anemia is more common in those who have a loss of a type of stomach cells, which results in a low level of intrinsic factor. The intrinsic factor is integral in aiding the human body with the absorption of vitamin B12. Most seriously, Pernicious anemia can increase a person’s risk of developing stomach cancer. This condition can be easily treated with vitamin B12 supplements, once the condition has been properly diagnosed.

Other possible symptoms caused by a B12 deficiency include:

  • Abnormal reflexes
  • Tingling, numbness, or other neuropathies
  • Impaired sense of position
  • Weakness in arms or legs
  • Dizziness, vertigo, or balance issues
  • Difficulty walking or abnormal gait
  • Confusion or memory loss
  • Dementia
  • Restless legs
  • Tremors
  • Vision problems
  • Incontinence
  • Impotence
  • Anger and irritability
  • Depression
  • Personality changes
  • Paranoia
  • Mania and/or psychosis
  • Hallucinations
  • Violent and antisocial behavior
  • General weakness
  • Shortness of breath or difficulty breathing
  • Fatigue
  • White appearance; pallor

B12 Shots for Weight Loss

Are B12 shots for weight loss effective? How do they work? How often do I need them? These are just a few of the many common questions those considering purchasing B12 shots for weight loss may have. This is understandable, considering there is an entire industry dedicated to dietary FADs and quick fixes. It can be hard to separate the scams from honest products when every social media influencer claims their rock-hard bodies are coming from a magical detox concoction.

However, it’s important to point out that B12 shots for weight loss aren’t injections containing something your body doesn’t usually contain – vitamin B12 is a crucial part of a healthy life! At this point, you may be considering a B12 shot for weight loss, but you need answers to the questions above. Let’s break it down.

Also read – 10 Things All Men Over 40 Should Know to Stay Healthy

Are B12 shots for weight loss effective? Simply put, it depends on what is affecting your weight management problem. Those suffering from B12 deficiencies can experience low energy, poor sleeping patterns, and decreased metabolic function. All of these factors can greatly impact your ability to lose weight. They lead to little motivation, an inability to turn food into energy, and negatively impact your mood. As losing weight is as much psychological and dependent on your mental health as physiological, alleviating these symptoms can positively influence an individual’s weight loss endeavors.

How do vitamin B12 shots for weight loss work, and how often do I need them? Vitamin B12 shots for weight loss typically require a prescription from your doctor and can be self-administered or given by a health care professional. If you are B12 deficient, the injection works by improving your consumption and absorption of B12 over a treatment period. While some people only need B12 shots to initiate the process of increasing their vitamin B12 levels, others require a consistent and possibly life-long daily dose if they suffer from a condition that causes a constant deficiency. Depending on your diet, health, age, and other medical factors, the frequency can range from daily or weekly injections to monthly or bi-annual shots. The frequency of treatment is decided by your doctor to serve your unique and specific health requirements best.

There are essentially two subgroups of B12 weight loss shots – pure, pharmaceutical-grade injections, and lipotropic injections. A lipotropic injection consists of various vitamins and nutrients such as vitamin B6, vitamin B complex, branched-chain amino acids (BCAAs), L-carnitine, phentermine, and MIC. While lipotropic injections do not require a prescription as the pure B12 injection does, it is important to note that there is a different set of risks and side effects associate with them.  Side effects and symptoms to be aware of include:

  • Anxiety
  • Constipation
  • Diarrhea
  • Dry mouth
  • Fatigue
  • Incontinence
  • Increase in heart rate
  • Insomnia
  • Numbness in feet or hands
  • Extreme fatigue
  • Gastrointestinal upset
  • Hunger pangs when coupled with an extremely low-calorie diet
  • Irritability
  • Jitteriness
  • Lightheadedness

B12 Shots for Weight Loss – Forms and Dosage

Pure B12 shots for weight loss come in four different forms: methylcobalamin, adenosylcobalamin, hydroxocobalamin, and cyanocobalamin. While they are all essentially very similar to one another, there are some differences in how the supplement is administered.

  • Methylcobalamin is an active form of B12 that works with several enzymes to create amino acids, produce red blood cells, repair DNA, and assist with other essential physiological processes. This form of B12 is typically administered through injections and oral supplements.
  • Adenosylcobalamin is very similar to methylcobalamin and typically reacts the same in the body. It should be noted that this form of a B12 supplement is very hard to find because the molecule is unstable.
  • Hydroxycobalamin is a natural type of vitamin B12 that is produced by bacteria in the digestive tract. Sourced from food, this form of B12 can be engineered in a lab but isolating it from test cultures. It is easily converted into the body and is the generic form of injectable B12 shots.
  • Cyanocobalamin is an artificial form of B12 that contains an inconsequential amount of cyanide – meaning it does not harmfully affect or negatively impact the human body. Cyanocobalamin is the most predominant form of oral, intramuscular, and intravenous B12 supplements.

The dosage for B12 shots for weight loss can range from 0.5 mcg daily to 2000 mcg daily. The dose is greatly dependent on age and the cause of a vitamin B12 deficiency. Dosage information and frequency can differ regarding the method of administering the vitamin.

Frequently Asked Questions

How does vitamin B12 support weight loss?

Vitamin B12 is associated with weight loss because of how it functions within the human body on a cellular level. Because vitamin B12 converts the food that is consumed into sugar and other forms of fuel, it helps to keep bodily processes running smoothly. B12 is also associated with promoting weight loss as it helps to boost both metabolism and energy levels.

Are B12 shots painful?

Most vitamin B12 injections are administered through a very fine needle; therefore, you can expect the same level of pain that you experience with other shots, possibly even less if the past injections you’ve received used a larger needle.

Are B12 shots for weight loss more effective than oral B12 supplements?

Typically, yes. Because supplements are ingested and absorbed through the digestive tract, they are subject to the acids in the stomach as this is how the human body breaks down food. While stomach acid breaks down food, it also diminishes the vitamins and nutrients within the food – allowing the body to only absorb a small amount. This is especially problematic for those who suffer from stomach and gastrointestinal conditions.

Considering a B12 Shot for Weight Loss?

Figuring out where to start looking for a high-quality B12 shot can be overwhelming, but the best place to start is at your doctor’s office. To treat weight management issues caused by a vitamin B12 deficiency, you need a proper diagnosis and a prescription.

If you and your healthcare professional determine that a B12 shot for weight loss will positively impact your health and the quality of your life, then it is time to consider where to get your B12 shot.

Invigor Medical offers pharmaceutical grade methylcobalamin with few side effects and many benefits! As an FDA-register compounding pharmacy, you can be assured that you are getting a trustworthy and high-quality product that will improve upon your weight loss efforts.

To learn more about Invigor Medical and how it can treat your possible B12 deficiency visit –

Also read – 7 Exercises for Older and Overweight Individuals


While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider.  You should always consult a practicing professional who can diagnose your specific case.  The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice. 


  • National Institutes of Health. (n.d.). Vitamin B12. Retrieved from
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Written by Riazzudin


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