Giving You Back YOUR Life

Does B12 deficiency affect blood pressure?

There was a recent article on confirming that blood pressure is sensitive to B12 deficiency.  But there were a few inaccuracies, so I thought I’d update the information.

High (and low) blood pressure are caused by a number of factors, the most obvious of which are the state of arousal (meaning any intense emotional state, and most usually in humans, anger or stress) and the balance of electrolytes.  The state of arousal causes the muscles of blood vessels (arteries are the ones which have muscular walls) to contract, squeezing the blood to higher pressure.  Electrolyte balance in the blood cause water either to flow into the blood stream or to flow into the surrounding tissue, so high levels of salt (sodium) in the blood cause more water to flow into the blood to try to dilute it, and low levels of salt (a medical condition called hyponatraemia which is often associated with being unable to string two words together) cause the opposite effect or dangerously low blood pressure.

Both are usually active responses, that is, the body does them when it decides they are necessary, although in the case of high electrolytes such as salt, too much salt in your diet can play a part.

So how does B12 affect this?

B12 has two effects on the cardio-vascular system: the first is through leaving homocysteine instead of converting it to SAMe; and the second is through the endocrine system.


Homocysteine is a natural amino acid which is important in the biochemical pathways for production of a group of amino acids which can’t be produced from other biochemical pathways.  Since amino acids are necessary for proteins and the building blocks of the body are proteins, if a whole group of amino acids can’t be produced then there is a problem.

However in the context of blood pressure and heart disease, high levels of homocysteine cause varicose veins, sclerotic arteries, and heart failure.

There’s too much homocysteine when there isn’t enough B12 to take the biochemical pathway forward to methionine, so homocysteine accumulates.

The Endocrine system

The hormones in the body, and their control, are called the endocrine system. The whole endocrine system is sensitive to B12 deficiency.  B12 is needed for the structure of cell membranes, and the cell membranes have to have the right structure so the pituitary gland can measure how much of each hormone is in the blood, and adjust as necessary.  Also the endocrine glands (the various parts of the body that produce hormones) are particularly susceptible to autoimmune attack, so B12 deficiency may result in the endocrine gland being damaged.

So a shortage of B12 can cause high levels of arousal hormones such as adrenaline, thyroxine or cortisol, resulting in high blood pressure (and a whole variety of heart diseases if left unchecked).  It’s more usual that a shortage of B12 results in low levels of these hormones so you feel tired all the time.

But some hormones, such as renin, angiotensin and aldosterone directly affect electrolyte balance and therefore indirectly affect blood pressure.

Blood Pressure and B12d

B12 deficiency can therefore cause high blood pressure, or very low blood pressure.  It’s worth taking B12 supplements, however it can take time for the endocrine system to heal after B12 deficiency so some people find they should have artificial endocrine supplements such as cortisol during the recovery period, as prescribed by a physician.

We know that you can’t overdose on B12, so you won’t do any harm by taking B12 supplements.  Some people do report that when they have B12 injections, they feel terrible because they don’t have enough potassium or magnesium or some other electrolyte; this does happen, and what we think is happening is that once the B12 is supplemented, then they can actually feel the effects of the low potassium (or whatever).  It was low before, but all they could feel was the low B12 until that was solved.  If you have been B12 deficient for a while, it’s worth taking a one-a-day multivitamin/multimineral to give yourself a general balance and if the rotten feeling persists then get a diagnosis from your doctor.

Return to B12d Charity Support Group Blog

Janette first appeared in the BBC InsideOut documentary in October 2006. Since then the NHS has forced her doctor to withdraw B12 replacement therapy on a number of occasions, and she tells of her struggles with having B12 and then having it taken away.
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Donna, like so many women, wants to live a normal life. Vitamin B12 could give her that chance.