B12 Shots: How Quickly Do They Work?

Individuals looking to increase their B12 levels to boost energy, immune function, or metabolism may be wondering, “How quickly does a B12 shot work?” Ultimately, this can depend on a number of factors, such as your current B12 intake and how effectively your body can process B12. Before we give you a possible time frame to expect your B12 shot to work, consider your relationship with B12.

B12 Intake

In general, vitamin B12 should be ingested through your daily diet. In an ideal situation, as your body uses B12, you are replenishing your B12 levels by eating foods that contain the vitamin, such as meat, fish, eggs, and dairy. In other words, you get B12 at the same rate you use it. This isn’t practical for individuals who suffer from chronic B12 deficiency or frequently deplete the entirety of their B12 stores. In those cases, the daily intake of B12 isn’t able to keep up with the B12 the body is using.

Who needs to take B12?

Vegans and vegetarians are particularly at risk for B12 deficiency because plant-based foods do not naturally contain vitamin B12. Individuals who have had gastric bypass surgery are also at risk due to alterations to the GI tract that impair the release and absorption of B12.

Low B12 levels can cause fatigue, weakness, shortness of breath, headaches, digestive changes, and other symptoms. Left untreated, a B12 deficiency can also lead to long-term health issues. 

If you need to recover quickly from an illness that depleted your B12 reserves or have recently discovered you have a B12 deficiency that is impacting your quality of life, one solution is to give your body a larger dose of B12 all at once. B12 given intravenously provide a concentrated dose of B12 directly to the bloodstream or muscle via injection. For someone who has difficulty getting enough B12 due to underlying health conditions or diet, this helps offset the need for smaller daily increments of B12 from diet or oral vitamins.

B12 Absorption

When we get B12 through our diet, absorption occurs during digestion. However, many factors can limit or even prevent proper absorption. This usually occurs in individuals with underlying digestive conditions, those who have trouble absorbing all nutrients through digestion, or those with pernicious anemia, which specifically prevents B12 absorption.

When your body does absorb B12, it takes time for the vitamin to be distributed throughout the body and more time for the body to use it in a way that is noticeable. These two delaying factors are why patients with low B12 levels are often prescribed B12 shots instead of oral supplements.

How Fast Does a B12 Shot Work Compared to Oral Supplements

Because B12 shots are administered intramuscularly and absorbed directly into the bloodstream, the nutrients bypass the slow digestive process. This is the main factor for how long a B12 injection takes to work, offering a significant advantage over oral supplements, which must be broken down by the digestive system before they can be distributed throughout the body.

In addition to impacting the speed of absorption of oral supplements, the digestive process also affects the extent of absorption, with 40%-50% of low-dose B12 vitamins being absorbable. In higher dose supplements, that percentage drops to 1%-2%. B12 injections, on the other hand, allow up to 100% absorption and immediate use by the body.

How Quickly Does a B12 Injection Work – The Short Answer

Most patients report feeling the effects of a B12 shot anywhere from 12-48 hours after treatment. Imagine how much longer that would be if you still had to ingest, break down, and absorb the B12 before the 12-48 hour period started.

Some patients, usually those with chronically low levels of B12, may notice results faster than this.

The Best Time to Take a B12 Injection 

If you have a big event coming up, such as finals week, a vacation, or a wedding, you might be wondering about the best time to take a B12 shot to ensure you feel the benefits when you need them. We recommend that you aim for an appointment one to two days before the date in question. This will give your body all the time it needs to effectively utilize the B12. However, if you have a more severe B12 deficiency, you may require additional treatments to reach optimal levels. In that case, the best time to take vitamin B12 injections would be seven to ten days prior and again one to two days before your event.

Conclusion

Healthy B12 levels rely entirely on effective B12 intake and absorption. For individuals who have difficulty eating foods that provide their body with enough B12, a B12 shot is an alternative that won’t compromise other dietary needs. If the issue lies with absorption, B12 shots or IV infusions are an effective alternative to oral supplements because they are administered via injection or intravenously, meaning they do not need to be absorbed through the digestive process. This allows for greater absorption and faster benefits. How long B12 shots take to work depends on your B12 levels when you receive the injection, but you can expect to see improved energy, mental clarity, sleep, and other benefits anywhere from 12-48 hours after treatment.

Book your B12 Injection today.

For more information on B12 shots, our other injection therapies, or help scheduling an appointment, find your closest Hydration Room location.