Sven Wombwell
Article by: Sven Wombwell
Estimated 7 minutes read
Quick summary
Vitamin B12 is essential in developing DNA, red blood cells, and nerve and brain cells and provides various health benefits.  Some symptoms of a vitamin B12 deficiency include depression, fatigue, altered moods and memory loss. B12 deficiency can result from diet or the inability to absorb nutrients properly. The benefits of B12 shots include that they work more quickly than supplements.

Vitamin B-12 is an essential nutrient that plays a vital role in maintaining good health, including developing red blood cells and the functioning of the nervous system. (1) B-12 injections are often prescribed to increase vitamin B-12 in people who may be deficient or have difficulty absorbing it through diet alone. This article will discuss the benefits of B12 shots, how much you need, and why getting enough is crucial for health.

What is Vitamin B12?

Vitamin B12 is a water-soluble vitamin also known as cobalamin. Essential for various hormonal and metabolic functions, it can naturally be found in various types of meat, offal, fish, and dairy products and also taken in supplement form. 

B12 Foods

As one of eight B Vitamins, B12 is responsible for producing digestive enzymes that help to convert the food we eat into glucose which we use for energy. 

Some of the functions B12 assists with include: (2)(3)

  • DNA synthesis 
  • Production of red blood cells
  • Conversion of protein and fats
  • Fetal development
  • Brain Health
  • Cardiovascular health
  • Hormone production

How Much Vitamin B12 Do You Need?

Various factors can interfere with the absorption of vitamin B12, so the average levels may not be what is average for you, so it's essential to pay attention to how you feel despite the numbers.

With that said, according to Cleveland Clinic, (4) the following are recommended daily amounts:

  • Infants to 6 months: 0.4 mcg
  • Babies from 7 to 12 months: 0.5 mcg
  • Kids from 1 to 3 years of age: 0.9 mcg
  • Kids from 4 to 8 years: 1.2 mcg
  • Kids from 9 to 13 years: 1.8 mcg
  • Teens from 14 to 18 years: 2.4 mcg
  • Adults 18 and up: 2.4 mcg

(Pregnant and lactating: 2.6 mcg and 2.8 mcg)

Signs of a B12 Deficiency

Even though B12 is an essential vitamin for health, many people don't get enough. Either they don't get adequate amounts through their diet, or their bodies can't absorb it, resulting in a vitamin B12 deficiency. According to a study (5), it's not uncommon to have lower than adequate amounts of vitamin B12 than what's required for normal functioning, but it doesn't come without risks.

According to Harvard Health, (6) factors related to a vitamin B12 deficiency include:

  • Limiting animal products in the diet

Vitamin B12 is naturally found in meat, poultry, fish, and dairy products, so individuals that don't eat animal products can often become deficient. To get what they need, it's vital to include B12-fortified foods or oral supplementation to meet vitamin B12 requirements.

  • Prescription medications

Some medications, including those for type 2 diabetes, may block the absorption of vitamin B12, leading to a deficiency.

  • Autoimmune disorders

Autoimmune diseases can attack the cells in the body, leading to problems absorbing vitamins. When the body can't absorb nutrients, a deficiency may result. 

  • Stomach acid

A lack of stomach acid, whether due to medications, health issues, or age, can interfere with absorbing B12 since stomach acid is necessary for the nutrients to enter the bloodstream. 

  • Digestive disorders

Some diseases that affect the digestive system can interfere with the digestion and absorption of vitamins and increase the risks of a deficiency.

What Happens When You Don't Get Enough B12?

Not getting enough vitamin B12 can cause neurological, physical, and psychological issues (7) and include:

Neurological Problems

  • Tingling of the hands and feet
  • Nerve damage
  • Numbness
  • Memory loss
  • Confusion
  • Speech problems

Physical Problems

  • Exhaustion
  • Weakness
  • Nausea
  • Loss of appetite
  • Diarrhea
  • Vomiting
  • Weight loss
  • Sore mouth
  • Erectile dysfunction
  • Headaches

Psychological Problems

  • Depression
  • Irritability
  • Not feeling like yourself

Diagnosing a vitamin B12 deficiency isn't easy because symptoms may be considered to be related to other health issues, so if you think you could be experiencing signs, it's crucial to talk with your health practitioner to get tested.

What if you have a B12 deficiency? Could vitamin B12 injections help?

A deficiency in vitamin B12 is called anemia and occurs when your body lacks healthy red blood cells. Since red blood cells carry oxygen to your organs and tissues, without them, your body won't work as efficiently as it should, which may lead to the various health issues discussed earlier. To treat a deficiency, your health professional may recommend vitamin B12 supplementation. 

What Are Vitamin B12 Shots?

Depending on the severity of the deficiency, it may be necessary to get B12 shots as they elevate the levels quickly. Vitamin B12 shots are typically available by prescription and administered into the muscle tissue about once a month.  

While vitamin B12 supplements are available over the counter, they are not effective for everyone. If you have absorption issues, you'll require a more aggressive approach to increasing levels. The benefit of B12 shots is they can protect health from various conditions.

One of the most significant benefits of B12 shots is the fact they are higher dosages than supplements. B12 injections are available in two forms subcutaneous and intramuscular.

What Types of B12 Shots Are Available?

Subcutaneous B12 shots are injections of Vitamin B12 given just beneath the skin layer. This method of administering B12 is generally preferred for individuals who require regular doses of the vitamin and may not be comfortable with intramuscular injections. The absorption of the B12 in this method is slightly slower than intramuscular, but it still provides a steady release into the bloodstream over time.

Intramuscular B12 shots are injections of Vitamin B12 that are administered into the muscle tissue, usually in the upper arm, thigh, or buttocks. This method is preferred for individuals who require higher doses of the vitamin, as the absorption rate is faster and more efficient. Intramuscular B12 shots are typically given to individuals with pernicious anemia or other conditions that prevent adequate absorption of Vitamin B12 in the gastrointestinal tract.

Benefits of B12 Shots

Although B12 supplements may be beneficial when you don't think you're getting adequate amounts through diet, some serious health issues can require quicker results, so vitamin B12 shots may be suggested to help with the following: 

  1. Reduce cognitive decline and depression.

According to a study (8), taking vitamin B12 can help alleviate problems with memory, elevate mood and prevent depression, especially in older adults. 

  1. Improves low sperm count.

According to a study (9), vitamin B12 might help to decrease oxidation damage and improve sperm count as well as decrease inflammation that can affect semen impairment.

  1. Reduce fatigue

Getting vitamin B12 shots can reduce the fatigue that comes with a deficiency. A study (10) showed that the higher dose can impact energy levels.

  1. Helps with fetal development

B12 deficiency can increase the chances of preterm birth, putting the baby at risk for developmental issues related to low birth rates. (11)

  1. Reduces risk of diabetic neuropathy

A study (12) showed that vitamin B12 could reduce the risks and improve symptoms of nerve damage caused by diabetes.

B12 and Testosterone

Vitamin B12 affects every system in our body, so it could also be a factor in testosterone levels. According to a study (13), the benefits of B12 shots may be due to increased functionality of reproductive organs and reduced oxidative damage to sperm. Since red blood cells are needed to send oxygen throughout the body (14), it makes sense that a deficiency can affect testosterone and sperm. 

While various vitamins can be linked to testosterone levels when you need additional assistance, testosterone replacement therapy can help.


For people at a higher risk of health-related issues connected to a vitamin B12 deficiency, the benefit of B12 shots is they significantly reduce symptoms. While a deficiency is most common among older adults and those with conditions that won't allow absorption, anyone can be at risk. Hence, paying attention to your health and eating a healthy diet is essential.

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