How Birth Control Affects B12 Levels

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There are endless stories of people claiming to have been suffering from incurable vitamin B12 deficiency, until their symptoms miraculously cleared when they came off birth control. Quite a few scientific studies also established a link, and now the idea that the Pill can cause a dramatic drop in B12 levels is everywhere.

Bad Science
The problem is that circumstantial evidence isn’t even bad science, let alone good science. It’s simply not science at all. Taking a few people who think that contraceptives caused their B12 deficiencies as irrefutable proof is hugely flawed. Hearsay doesn’t mean anything in the real world.

Right Wrong Good BadAs for the scientific studies? Well, they really did find a connection between oral contraceptives and low blood levels of B12. But these studies were mostly done in the 1980s, 30+ years ago. They often employed poor methods that would be laughed out of the lab nowadays. Plus more recent, more rigorous research doesn’t agree with the conclusions.

What’s more, it can be argued that the outdated research of the 1980s isn’t even relevant to the present situation. Oral contraceptives in the past contained far more estrogen than they do today, which means the results of those tests wouldn’t be applicable even if they weren’t flawed.

Recent Research
All the latest evidence suggests that taking modern oral contraceptives doesn’t affect your chances of suffering from B12 deficiency. It’s true that there are still plenty of health problems associated with the Pill, but this isn’t one of them.

Does Birth Control Have Any Effect On B12 Levels?Science
Interestingly enough, there’s still a fair bit of evidence that using the Pill does indeed lead to lower levels of vitamin B12 in the blood. In fact, one study found that even taking B12 supplements didn’t improve the situation.

But before you shout me down, this doesn’t actually have to be a contradiction – it turns out that low blood levels don’t necessarily translate to a deficiency.

So What The Heck Is Going On?
No one’s absolutely certain why this happens yet, but it seems that the low levels of B12 that are routinely measured in women taking oral contraceptives are due to a redistribution of the vitamin, rather than a deficiency.ID-100188412

This means that while standard blood tests might suggest that your body’s supply of vitamin B12 is dangerously low, it might not actually be a problem. Your cells are probably getting all the B12 they need, just via a different mechanism.

Another idea is that the reduced blood levels could be due to a decrease in certain proteins that bind to B12. Again, not a problem, but it might look like it should be one on the surface.

Where’s The Evidence?
One of the many important roles played by B12 is reducing levels of homocysteine in the blood. Homocysteine is an alpha-amino acid, and having lots of it is thought to be a risk factor for both coronary artery disease and dementia.

In patients with vitamin B12 deficiency, Evidence Proofmeasured levels of homocysteine tend to be worryingly high. The same is true of another chemical called methylmalonic acid.

The healthy levels of these substances in women taking oral contraceptives suggests that they’re not suffering from B12 deficiency. In fact, it suggests their B12 levels are nothing to worry about at all, even if direct measurements might hint otherwise.

So I Don’t Need A B12 Supplement?
If the only reason you thought you might was because you were taking an oral contraceptive pill, then no, you probably don’t. Even official bodies like the National Institutes of Health don’t consider women taking contraceptives to be at risk of B12 deficiency.

If you do fall into one of the high risk categories for B12 deficiency, you  should be taking a supplement regardless of your chosen method of birth  control. This includes vegetarians and vegans, who often can’t get enough  B12 from food alone. (And by the way, there aren’t any vegan oral  contraceptives anyway!)

Plenty of people take dietary B12 supplements just to be on the safe side,  and you can see the supplements we recommend here. Obviously  whether or not you want to boost your intake is a personal choice, but  contraceptives shouldn’t play any part in the decision.

If you have any doubts whatsoever about whether to take a supplement, please take a quick look at our dedicated article Do You Need A B12 Supplement?

From top to bottom, images are courtesy of digitalart, renjith krishnan, cooldesign, and Simon Howden, all at

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