Vitamin B12: Uses & Dosage, Deficiency, Side Effects & Health Benefits

Vitamin B12 is an essential nutrient for your health, but you don’t produce it naturally. As a result, you have to rely on food to get your daily needs.

B12 is part of many important processes in your body. From the normal functioning of nerve cells, to creating DNA and red blood cells, B12 plays a part. Most people know about it as the energy vitamin – but that doesn’t quite do B12 justice.

Simply put, the B vitamin family is integral to your entire metabolism. B vitamins are there to keep your eyes, skin and hair healthy too.

Without enough vitamin B12 your body can’t work properly. Deficiency can even leave you feeling fatigued, tired and depressed. You might notice a change in your appearance too, as a lack of red blood cells impacts your skin, hair, and nails.

Healthy levels of B12, however, can help you to thrive. You’ll be able to get the most out of the food you eat, and your cells should be happily supported. So, it’s important to be mindful of how much B12 you’re getting from the diet and supplements. It isn’t optional – but – integral – for living your best life. Keep reading to find out how it might even help weight loss.

What is Vitamin B12?

Vitamin B12 is an essential nutrient your body can’t make itself. What you eat and drink determines how much of the powerhouse micro you get.

More specifically though, B12 is a water soluble vitamin, that’s also known as cobalamin (1). It’s naturally found in animal foods like fish, meat, and eggs, so you should get enough from a well-balanced omnivorous diet.

Because its only found in animal products, vegans are at a higher risk of deficiencies. That’s one of the reasons that foods such as bread, plant milks, and cereals are fortified with B12. This version is always synthetic and made in a lab – most are certified vegan.

Having the right amounts of vitamin B12 can keep you energized and focused. It can also help prevent heart disease and boost your memory. Yes, that’s on top of all the previously mentioned benefits. B12 works hard to look after you.

Alarmingly though, a lot of us are B12 deficient. This could be because of how little someone eats, or how well they can absorb the vitamin itself.

One thing to remember is that vitamin B12 is water soluble. So, if you end up taking in too much, your body can’t store it. You’ll naturally pass the B12 you don’t need in your urine, providing you haven’t been given a B12 injection.

What does Vitamin B12 do?

Vitamin B12 is involved in the metabolism of every single cell in your body. It’s required for DNA synthesis, as well as for the metabolism of fatty acids and amino acids. Put plainly, you need it to create certain DNA, as well as unlocking energy from the food you eat.

One of B12’s most important roles is helping your central nervous system function properly. It does this by aiding the synthesis of myelin, the protective sheathe that covers your nerves, and acts like a layer of insulation.

Red blood cell and bone marrow production also relies on vitamin B12. Without it, the DNA that instructs red blood cells to be completed and divide isn’t created (2).

Your body uses red blood cells to transport oxygen around your body. Therefore, B12 is a key contributor to your energy levels.

Women who are B12 deficient often say they feel fatigued and tired. This is because not enough oxygen can go to their vital organs, which leaves them drained.

Because it has a role in cellular metabolism, vitamin B12 supports your mood too. It does this helping to create serotonin – the feel-good hormone that regulates mood.

As you can see, there’s not much vitamin B12 doesn’t do. That’s why it’s vital your levels are always topped up.

Recommended Intake of Vitamin B12

The recommended daily intake of vitamin B12 is 2.5 mcg for adults (3). Women who are pregnant are advised to take 2.6 mcg and lactating women should take 2.8 mcg.

Some supplements, however, might go over this amount to keep you safe from deficiencies. We’ve put a whole 2.4ug in Hourglass Fit to keep you energized and healthier while dieting.

Eating a wholesome, well-balanced omnivorous diet should be enough to meet your daily amount of B12. But if you’re dieting to lose weight, it can become harder to get enough B12 from food. That’s why we’ve added plenty to the Hourglass Fit formula.

Vitamin B12 deficiency

Even though vitamin B12 is found in a lot of foods, deficiencies are still common. Some people are more at risk than others as well.

Those more likely to develop a B12 deficiency are the elderly, strict vegans, and bowel surgery patients. People taking the drugs metformin or antacid are included in this at-risk group too.

Diagnosing a vitamin B12 deficiency isn’t always easy. Sometimes it could take months for the symptoms to show up.

Occasionally, doctors can mistake vitamin B12 deficiency for a lack of folate – aka vitamin B9. Fixing a folate deficiency won’t automatically stop the symptoms of having low B12, so it’s best to keep on top of both.

You might only start to suspect a vitamin B12 deficiency once you get one or more symptoms. That’s why it’s a smart move to know them, so you can recognize problems early.

These are the most common signs, symptoms, and side-effects of low B12.

Signs/Symptoms of Vitamin B12 deficiency

1. Fatigue

Feeling fatigued and weak is common for people with low B12.

Remember how we said vitamin B12 was super important for red blood cell production? That’s why low amounts can make you tired and weak.

Basically, because your body doesn’t have enough B12 to make red blood cells, not enough oxygen can be transported around your body. It simply needs red blood cells to carry it.

Anemia is the proper medical term for this issue. Symptoms can go from mild to severe too, depending on how bad your condition is.

Fortunately, if anemia is caught early, treatment could be as simple as taking a B12 supplement.

2. Mood Alterations

Another reported side effect of vitamin B12 deficiency is mood changes.

One theory is that low B12 levels result in the body producing high amounts of homocysteine. This amino acid can then harm your brain tissue and interfere with neurotransmitters.

Scientists call this the “homocysteine hypothesis of depression” (6)(7)(8).

High levels of homocysteine can be caused when B12 drops too low to help manage it. Folate and vitamin B6 deficiencies can be part of the problem too.

There is research out there that says supplementing can reverse these symptoms (9)(10). One study even saw a dramatic resolution of cognitive impairment after B12 was given to a 21-year old patient (11).

It’s important to remember, however, that B12 deficiency might not always be the cause of these complications. Mental health issues can stem from a wide variety of factors – if you’re ever unsure, speak to your doctor.

3. Pale Skin

Many people who experience a vitamin B12 deficiency notice their skin becomes pale.

Remember how there wasn’t the right type of DNA made to direct red blood cells division? One thing that can happen is megaloblastic anemia, where the red blood cells in your bone marrow are too big and fragile.

As a result, they can’t pass freely into the bloodstream and circulate around your body. Pale skin can be is a sign of this happening.

4. Jaundice

Jaundice is a condition where your skin and eyes become yellowish.

Because the red blood cells trapped in your bone marrow are so fragile, they often break down. When this happens, it can cause a buildup of bilirubin – a red (or sometimes brown) substance.

Your liver actually produces bilirubin when it breaks down old blood cells. Normally, this isn’t an issue.

However, in high amounts, bilirubin buildup can make your skin and eyes appear yellow (12).

5. Pins and needles

A lack of vitamin B12 can mean you don’t produce enough myelin, the fatty substance that protects and insulates your nerves. Unfortunately, this can lead to a more severe side effect of B12 deficiency – nerve damage.

Myelin allows your nervous system to work properly. Without it, electrical impulses can’t travel efficiently.

If your nervous system isn’t firing right, you might start to feel paresthesia. You’ve most likely experienced this as the tingling of pins and needles.

Studies have shown pins and needles to be a common symptom of B12 deficiency (13). You might even experience them without any signs of anemia too (14).

In this section, we’ve only looked at a handful of the main symptoms of B12 deficiency. Other complications include:

  • Dizziness
  • Being short of breath
  • Mouth ulcers
  • High temperature
  • Vision problems

Health Benefits of Vitamin B12

Having healthy levels of all the essential nutrients lets you live your best life. Naturally, there’s more than a handful of health benefits from vitamin B12.

1. Improved Mood

Like we mentioned earlier, B12 plays a big part in synthesizing and metabolizing serotonin. So, getting the right amounts could keep you in a good mood.

Also known as the happy chemical, serotonin has roles in regulating your appetite and emotions. It’s also behind certain motor, autonomic, and cognitive functions too.

It’s not quite clear how serotonin actually affects these functions. Low levels, however, have been connected to depression.

According to research, B12 deficiency can even double the risk of severe symptoms (15). Plus, one study showed that people who took both antidepressants and B12, showed more improvements than those that took antidepressants on their own (16).

As you can see, studies support the idea of using vitamin B12 supplements to tackle symptoms of depression. While it might not be the case every time, fixing a deficiency could make significant differences to your mood.

2. Energy

Healthy levels of vitamin B12 might also help you to feel energized.

However, it’s not because B vitamins alone give you energy. It’s more to do with their ability to support your metabolism and your ability produce energy (17).

There’s no hard evidence that a supplement will elevate energy levels if you’re already sufficient, though (19).

3. Healthy hair, skin and nails

We already know that low vitamin B12 levels can cause problems for your skin. But what about your hair and nails? Other B12 benefits include:

B12 deficiencies can result in lots of dermatologic issues, ranging from patchy skin, through to nail discoloration and hair changes. It can even make your mouth inflamed with painful, cracked corners (20)(21).

Bottom line – getting enough B12 every day helps to keep your hair, skin and nails looking their best.

Other B12 benefits include:

  • Could support brain health
  • May help heart health
  • Could reduce risk of macular
  • Degeneration
  • Might aid weight loss

Side Effects

Vitamin B12 taken at recommended doses shouldn’t cause side effects. That’s why we’ve used a sensible 2.4ug in Hourglass Fit – and in a form you can take by mouth.

Plus, B12 is a water-soluble vitamin so what you don’t use is passed out naturally. Even if you took slightly more than the recommended dose, you shouldn’t need to worry.

This isn’t true for vitamin B12 injections, however. These can have possible side effects, which is why they should only be given by a medical professional.

As with any supplement, there’s always a risk that you might be allergic to B12. If you’re in any way unsure, you should check with your doctor.


It’s natural to have questions when learning about a new supplement. So, we’ve put together the most frequently asked questions about B12 for you here.

As always, if we don’t touch on something you want to know, get in touch. Feel free to comment or email any queries you have.

Does vitamin B12 help you lose weight?

B12 supplements are quite popular in the weight loss world. But, there’s no evidence to show that they alone cause weight loss.

Instead, what B12 can do is help you to feel energized enough to exercise. Supplements can also be there to make sure you get your daily needs when you’re eating less food.

Plus, all B vitamins play pivotal parts in regulating your metabolism. Deficiencies can make it harder to lose weight by making you fatigued, unable to utilize food, and left with a low mood. Sticking to your exercise routine and diet can become a lot harder. It’s important to remember that weight loss happens because of positive lifestyle changes. Vitamins and supplements alone can only support your hard work. It’s up to you to stick to your diet and be active – we are there to help along the way.

Which foods are high in B12?

Fortunately, there are so many vitamin B12 rich foods to choose from.

You’ll mainly find B12 in animal products such as meat, fish, and dairy. But that doesn’t mean vegans need to panic, because there’s an ever-growing list of B12 fortified options out there too.

Below is a list of nourishing, B12 rich food sources:

  • Organ meat
  • Clams
  • Beef
  • Dairy Products
  • Eggs
  • Fortified bread and cereal
  • Sardines
  • Fortified nutritional yeast
  • Fortified plant-based milks

Can vitamin B12 cause weight gain?

Taking vitamin B12 shouldn’t cause you to gain weight. That being said, if you’re deficient, you might notice your weight increase as you find your appetite again.

Try not to see this as a bad thing. It is much healthier to gain a little weight and get rid of your deficiency than to risk the symptoms.

Can vitamin B12 cause acne?

One study says too much vitamin B12 could cause acne if you’re prone to it. However, the study that was carried out used B12 injections, not an oral dose (22). Most vitamin B12 you can buy will be oral doses. For example, Hourglass Fit uses capsules to deliver our hand selected nutrients to your body.

Plus, there’s also research that suggests taking B12 won’t cause acne or make it worse. So, don’t worry just yet, the evidence isn’t conclusive.

Does vitamin B12 cause anxiety?

While vitamin B12 won’t cause you anxiety, a deficiency can. Low levels of B12 have been linked to numerous psychiatric symptoms.

Does vitamin B12 speed up your metabolism?

B vitamins are really important for keeping your metabolism functioning. Without them, your body finds it harder to process carbohydrates, fats, and protein for energy.

In short, B vitamins help turn food into energy. So, by getting enough B12, you can make sure your metabolism is always working its best.


Vitamin B12 plays a huge part in keeping you healthy. It’s one of the most important things for your metabolism and nervous system, and without it you experience a lot of health risks.

Keeping your B12 topped up can help you feel energized, motivated, and happy. Not only does it protect the cells in your body, but right down to your DNA too. Unfortunately, though, vitamin B12 deficiencies can be common. They can leave you feeling run down, sick, and sometimes with serious conditions.

That’s why we have added a generous and sensible dose of B12 to Hourglass. We want to support you in every way we can during your weight loss journey – and that starts with your health.

Good luck on your journey.

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