Woman experiencing fatigue due to B12 deficiency and wondering how long it takes to recover

How long does it take to recover from vitamin B12 deficiency?

Medically reviewed on January 9, 2023 by Morgan Spicer, Medical Communications Manager. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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Like many other nutrients, vitamin B12 is critical for human health and development and if you don’t consume enough of it from food or supplements, you could be a candidate for developing vitamin B12 deficiency [1].

Mild to moderate deficiencies of vitamin B12 are fairly common, with about 40% of people in Western populations reported to experience them [1]. But whether you suspect that you’re low on B12 or you’re currently in remission from a B12 deficiency, waiting for symptoms to dissipate can feel frustrating. The length and quality of your recovery process depend on the severity of your condition, but it can be immensely helpful to have some more insight into what to expect from the process.

Below, we’ll break down some B12 basics, signs and symptoms of a B12 deficiency, and what to expect from treatment so you can look forward to feeling like your energetic self again.

What is vitamin B12?

Vitamin B12 is one of eight B vitamins your body needs to make energy, form red blood cells, and perform other critical tasks [2]. The B vitamins (and their names) are:

  • B1 – Thiamine
  • B2 - Riboflavin
  • B3 – Niacin
  • B5 – Pantothenic acid
  • B6 – Pyridoxal 5’-phosphate
  • B7 – Biotin
  • B9 – Folate
  • B12 – Cobalamin

While each B vitamin plays a variety of important roles, vitamin B12 is critically important for three key physiological processes [1]:

  • Central nervous system development, protection, and function
  • Healthy formation of red blood cells
  • DNA synthesis

Despite being indispensable for some essential functions, the human body doesn’t make vitamin B12 on its own. Instead, humans have to acquire B12 through food sources, taking supplements, or receiving injections from a healthcare provider when they suspect a low Vitamin B12 level.

So you might be wondering: how much vitamin B12 should I take daily? Health experts’ recommended daily allowances (RDAs) for B12 intake recommendations vary by age, but the recommendations are the same regardless of your sex [1]:

  • 0 to 6 months – 0.4 mcg
  • 7 to 12 months – 0.5 mcg
  • 1 to 3 years – 0.9 mcg
  • 4 to 8 years – 1.2 mcg
  • 9 to 13 years – 1.8 mcg
  • 14 years and older – 2.4 mcg

If you’re pregnant, the National Institute of Health recommends you ingest at least 2.6 micrograms of B12 per day; if you’re breastfeeding, 2.8 micrograms.

What are the signs and symptoms of a B12 deficiency?

If you don’t get enough vitamin B12 or you have low B12 absorption, your body will start to respond. But before we get into the vitamin B12 deficiency signs and symptoms, let’s define those two terms [3]:

  • A symptom is a subjective marker that you (the patient) observe and report to a healthcare provider; for example, a headache.
  • A sign is an objective evidence that a healthcare provider can use to confirm your diagnosis and rule out incorrect diagnoses; for example, a positive or negative test result.

If you don’t get enough B12 in your diet or through supplementation, you may develop one or more of the following symptoms [4]:

  • Mild fatigue during exercise or daily activities
  • Heart palpitations
  • Skin paleness or hyperpigmentation
  • Glossitis (tongue inflammation)
  • Neurological symptoms such as loss of reflexes, loss of proprioception (knowing where your limbs are without looking at them), forgetfulness

Signs that healthcare providers use to detect a B12 deficiency include [4]:

  • Megaloblastic anemia (abnormally large and nucleated red blood cells)
  • Abnormal blood work, including decreased levels of haptoglobin; high levels of lactate dehydrogenase; and increased reticulocyte count
  • Severe neurological symptoms

It’s important to note that the severity of the symptoms above depends on the extent of your B12 deficiency. If you’ve had a chronic, severe vitamin deficiency for many years, your symptoms will be more significant than they would be after a few weeks of decreased B12 intake.

How long does it take to recover from vitamin B12 deficiency?

If your healthcare provider detects low B12 levels, they’ll tell you how you can expect to see symptoms persist after you’ve begun their treatment protocol.

B12 deficiency is typically treated in one of two ways, and some providers use both methods simultaneously [4]:

  • Intramuscular injection (a shot containing 1 mg of vitamin B12)
  • A prescription for a high-dose oral vitamin B12 supplement

But how long to recover from vitamin B12 deficiency after each treatment? The amount of time it takes for either treatment to take effect depends upon the severity of your B12 deficiency, and on the resulting health impacts of being deficient [4].

If you have only mild symptoms of B12 deficiency, you should notice the effects of treatment relatively quickly. For instance, if you’ve only noticed mild fatigue, and your provider treats your deficiency with an intramuscular injection, you should notice an improvement in just a few days.

The same is true if your blood work only shows signs of mild abnormalities: high levels of reticulocytes (immature red blood cells), homocysteine (an amino acid broken down by vitamin B12), or methylmalonic acid (MMA, a byproduct of amino acid breakdown) should subside after just a few vitamin B12 injection treatments.

What to do if you suspect a B12 deficiency

If you’ve noticed some mild symptoms of a vitamin B12 deficiency, it’s important to consult with your healthcare provider to rule out other possible causes. Following that, you’ll want to take the following steps under their supervision [5].

Get tested

If your healthcare provider suspects a vitamin B12 deficiency, they’ll likely suggest a blood test to examine:

  • Your levels of B12 and other essential nutrients
  • Common markers for vitamin deficiencies
  • Your complete blood count (CBC)

If you decide to proceed with testing, you can make an in-person appointment with a nearby testing facility.

Discuss your results with a healthcare provider

No matter which testing option you use, the next step is to review the results with your healthcare provider.

When you discuss your test results, your provider will [5]:

  • Examine the data – Your provider will outline the quantitative results of your test. This includes your B12 levels, the levels of other markers for B12, and your CBC numbers.
  • Interpret the data to make a diagnosis – Your healthcare provider will come to a conclusion about the underlying cause of your symptoms based on the data provided by your test. If they’re still stumped, they may recommend additional testing to rule out other causes.
  • Recommend treatment – If your provider can get to the bottom of your concerns with the results of your test, they’ll make a treatment recommendation that addresses the underlying cause of your symptoms. So, if your test results confirm a vitamin B12 deficiency, your provider may recommend an intramuscular injection, oral supplementation, dietary changes, or something else.

Seek treatment

If you have a B12 deficiency, your healthcare provider may recommend one or more of the following treatment protocols [1]:

  • Vitamin B12 injection – For some patients, the root cause of their B12 deficiency is their body’s difficulty in absorbing and retaining the B12 they consume through food. Injections bypass barriers to absorption. Patients who receive this treatment may receive just one injection or multiple shots over time.
  • High-dose oral B12 treatment – Instead of taking the injection route, a provider may prescribe a high-dose B12 oral treatment—a pill, capsule, or lozenge containing a higher concentration of B12 than your average over-the-counter (OTC) supplement.
  • Dietary changes – Your provider may recommend some simple dietary changes to help you get more B12 every day, either as a standalone regimen or in tandem with the treatments mentioned above. They may recommend foods with high levels of B12 (like dairy products or fortified cereals) or a daily supplement containing B12.

Continue to monitor your health

As you proceed with treatment, your provider will likely ask you to keep track of your symptoms and whether they recede. You could do this in a variety of ways:

  • Regularly journaling about your symptoms or your overall well-being
  • Writing down estimates of how much B12 you’re consuming throughout the day
  • Learning more about your own health using at-home tools and resources

And, if you don’t notice an improvement, check in with your provider—they may be able to offer more insight to help you get to the bottom of your symptoms.

Everlywell: exceptional care that meets you where you are

Whether it’s a suspected vitamin B12 deficiency or nausea that won’t let up, it’s not uncommon to avoid taking action on our health because of sheer inconvenience. But your well-being should never feel like a headache—and with Everlywell's vitamin B12 supplements, it's easy to get this key nutrient (as well as a range of other vitamins and supplements).

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  1. Vitamin B12. NIH Office of Dietary Supplements. URL. Accessed December 8, 2022.
  2. B vitamins. MedlinePlus. URL. Accessed December 8, 2022.
  3. Sign or symptom. National Center for Biotechnology Information. URL. Accessed December 8, 2022.
  4. Langan RC, Goodbred AJ. Vitamin B12 Deficiency: Recognition and Management. American Family Physician. 2017;96(6):384-389. URL. Accessed December 8, 2022.
  5. Alex Ankar, Kumar A. Vitamin B12 deficiency. National Library of Medicine. URL. Published August 12, 2022. Accessed December 8, 2022.
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