Are Vitamin B12 Injections Safe with MTHFR?

Vitamin B12 injections are primarily used to treat pernicious anemia and vitamin B12 deficiency. Injections may be given to people who have malabsorption issues due to disorders such as Crohn's disease, atrophic gastritis, chronic pancreatitis, and intestinal bacterial overgrowth. ³ Vegans and vegetarians may also require B12 treatment, especially vegan women who are pregnant or breastfeeding.

B12 shots are not given to help with weight loss, and they are unlikely to cause you to lose weight. 

In the US, Vitamin B12 shots are available as a synthetic version of vitamin B12 (cyanocobalamin). In the UK, injections are usually given as hydroxocobalamin or cyanocobalamin. It is typically an intramuscular injection in the arm, and is given by a nurse or a doctor.

Some naturopathic practitioners in the US may also offer methylcobalamin injections or IVs. Be sure to check which form of B12 is used in the injection.

B12 shots are recommended for people who are deficient in B12. If you have been diagnosed with low B12, your doctor may prescribe Vitamin B12 shots. 

However, some people may not be suitable for B12 injections. This includes children or those who are allergic to cyanocobalamin or cobalt. If you have had Leber's disease (or other forms of optic nerve damage), an iron or folic acid deficiency, or low potassium, your doctor may not recommend it.

Women who are pregnant or breastfeeding should also get advice from their doctor before receiving B12 injections.

Some people may experience side effects following injections with the cyanocobalamin form of B12, such as nausea, headaches, vomiting, itching, and dizziness. 

Side effects are not common with methylcobalamin injections, but it’s possible to have some pain and redness in the injection area. Injections are usually given in the upper arm, the bottom, or in the upper thigh. Some people may also experience adverse effects like mild diarrhea, itching, or a swelling sensation in the body. 

In rare cases, intramuscular B12 may cause a drop in potassium. If you experience muscle cramps, weakness, or an irregular heartbeat, consult your healthcare professional.

Injections may be given every month until B12 levels have returned to normal. When starting treatment, injections may be given weekly for 4-8 weeks. Once B12 levels improve and you are no longer deficient, your treatment may be switched to supplements.

The MTHFR genetic mutation has a negative effect on B12 absorption, with studies showing an increased prevalence of low blood levels of vitamin B12 in those with the mutation. The C677T variant is significantly associated with a decrease in intestinal absorption of vitamin B12. ⁴

Folate (vitamin B9) deficiency is also common in those with MTHFR. However, supplementing solely with folic acid/folate can mask an underlying B12 deficiency. This is because folate supplementation may improve symptoms to the point that the B12 deficiency is not detected in tests, and therefore is not treated. 

B12 plays an important role in the recycling of N5-methyl THF (the storage form of folate) to THF, the form of folate that serves as a coenzyme for numerous metabolic reactions involving amino acids and nucleic acids. B12 deficiency can impair this process and prevent the use of storage form of folate when needed, resulting in functional folate deficiency. ⁵ This can have significantly detrimental effects on the nervous system, cell division, and other methylation processes.

Deficiency of folate with or without vitamin B12 deficiency impairs DNA synthesis, leading to cell death, ineffective red blood cell production, and anemia. Hemolytic anemia may be more prevalent in patients with both MTHFR and B12 deficiency. ⁶

Reduced levels of B12 and folate compromise the body’s ability to convert homocysteine to methionine, leading to elevated homocysteine. This, in turn, can increase the risk of blood clots and cardiovascular issues. 

Low methionine levels can affect the production of A-adenosylmethionine (SAMe), a major methyl donor for the central nervous system and an essential nutrient required for the production of neurotransmitters. This can lead to cognitive impairment and mental illness. ⁷ 

For those with a B12 deficiency and an MTHFR mutation, one major advantage of B12 injections is that they are readily absorbed in the body and do not have to be taken as often as oral tablets. 

However, the bioavailability of the B12 injection depends on the form used. Synthetic B12 (cyanocobalamin) is less bioavailable by comparison and requires a three-step process to be converted to usable B12 in the body. ⁸

One study compared the effectiveness of sublingual B12 with B12 injections for raising levels in patients with vitamin B12 deficiency. The results showed that while both methods are effective, sublingual vitamin B12 is actually more efficient in raising b12 levels than injections, especially in patients with very low levels.⁹ The researchers also noted that sublingual B12 has many practical advantages over injections, which are painful, costly, and require repeated clinic visits. Additionally, sublingual B12 bypasses intestinal absorption issues, and is a more accessible treatment option for vitamin B12 deficiency. ¹⁰

Research also suggests that those who have genetic mutations may boost their B12 levels more effectively by taking natural forms of B12. ¹¹ It’s also important to note that taking B12 in combination with vitamin B6 and folate (rather than alone) is shown to be most effective for regulating homocysteine levels for some patients and preventing the combined risk of stroke, myocardial infarction (heart attack), and damage to heart cells. ¹²

Supplementing with folate, vitamins B6 and B12 is also shown to help lower homocysteine concentrations in patients affected by recurrent pregnancy loss (such as miscarriages) as well as MTHFR mutations. ¹³

The right form of these nutrients is crucial, which is why many MTHFR patients are directed to the Methyl-Life® product range. 

Methyl-Life’s® Methylated Multivitamins contain both  L-Methylfolate and active B12. Each Multivitamin is made with internationally-patented Magnafolate® PRO, which is clinically recognized as one of the purest methylfolates available and able to bypass the MTHFR mutation. The active B12 is provided by Hydroxocobalamin, which is readily absorbed and utilized in the body. ¹⁴

While B12 injections do work, sublingual vitamin B12 is proven to be more efficient in boosting B12 levels, especially in patients with very low levels. ¹⁵ Sublingual B12 is also much more affordable than injections, and avoids the pain and cost of repeated clinic visits. Sublingual B12 bypasses intestinal absorption issues and potential barriers caused by genetic variants, which makes it a more accessible treatment option for vitamin B12 deficiency.

Pros

• Easily absorbed: Sublingual B12 tablets are absorbed into the bloodstream through the mucous membranes when placed under the tongue. This means they bypass the digestive system and any malabsorption issues. The most bioavailable forms of B12 are methylcobalamin, hydroxocobalamin, and adenosylcobalamin. These are readily absorbed and utilized by the body. These forms can be taken in tablet form.
  
  
• Convenient: Sublingual B12 can be purchased OTC and taken at home, without a prescription.
  
  
• Painless: Tablets are non-invasive: no needles involved.
  
  
• Cost-effective: Sublingual B12 can be easily purchased online or in stores, and it is generally more affordable than prescription injections.

Cons

• Variation in quality There are hundreds of B12 supplements available now, and it can be difficult to know which works, or which is best for you. Quality can vary significantly between different brands, depending on the form and the manufacturing process.

• Taste: Many sublingual B12 supplements are flavored to improve the taste. It’s worth noting that cheaper supplements may contain artificial additives or sweeteners. 

• The absorption rate varies, but improvements in symptoms can often be observed within a week or two of starting supplementation.

Pros

• Injections deliver B12 directly into the muscle, where it is absorbed rapidly into the bloodstream. This method bypasses the digestive system that can compromise absorption. It also helps to correct severe deficiencies very quickly (if the deficiency is not based on genetic abnormalities which may require a specific form(s) of B12).
  
  

Cons

• Painful: B12 shots can be painful for some people, and very unpleasant for those who are afraid of needles.
  
  

• Clinic visit: B12 injections can only be given by a doctor or nurse, which requires a clinic visit. This can be time consuming and costly. Initial treatments may require several injections per week, followed by maintenance doses every month.
  
  

• Form of B12: Many clinics use cyanocobalamin (a synthetic form of B12 which requires a number of conversions) for their B12 shots.