Blood Pressure Rises When I Receive B... - Pernicious Anaemi...

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Blood Pressure Rises When I Receive B-12 Shot

Here is my anemia backstory; I was first diagnosed with anemia about 4 years ago. I had been chewing on ice and someone told me it was a symptom of low iron. I had been exhausted for sometime but I just attributed it to getting older. I started taking iron supplements and my iron levels went up but I was still exhausted and could barely climb 2 flights of stairs. I started having other weird symptoms, dizziness, difficulty catching my breath, numb toes, the tip of my nose was very cold all of the time, even in the summer. I went to my doctor because the numb toes were freaking me out. He told me to go to a podiatrist who told me I needed shoe inserts. That was such a waste of time and money.

I did some online research and saw that these were symptoms of low B-12 levels. I went to my doctor and asked him to test my B-12 which he did, to humor me. My B-12 was at 132. My doctor didn't think that was too low and told me to start eating more meat and liver, which I did. When I went back three months later my B-12 level was at 97. He started me on B-12 shots twice a week for 6 weeks. He called this the loading phase. Well, I went from normal blood pressure to high blood pressure almost immediately. I kind of didn't care because the B-12 shots made me feel so darned good. I swear I could feel my body perk up almost as soon as I got a shot. My nose stopped being cold, I got back some feeling in my toes. Unfortunately, I think some of the nerves are permanently damaged. I can walk up and down stairs without difficulty and I don't fall asleep on the sofa as soon as dinner is over. My blood pressure seems to be back to almost normal now that I am out of the loading process and am receiving a regular shot once a month.

Anyway, the point of this post is to ask if anyone else had their blood pressure go up when they started taking B-12 shots. My doctor said he has never heard of this side effect.

10 Replies

Hi MoKayD I've been having B12 injections for over 45 years and apart from an occasional heart "flutter" immediately after I have not had any problems with BP in fact I'm always on the "low side".

Do you know what your Folate level is as this and B12 help your iron to make red blood cells

It's good to read that you feel so much better and I wish you well.

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Blood pressure can be raised by all sorts of things and also varies with time of day. Was it consistently higher for a significant period of time?or was it raised at very spaced out intervals?

Not something I'd personally associate with B12 loading shots but we are all different.


Prior to B12 injections I had always had low to normal blood pressure. The nurse at my work was giving me my B-12 shots and she always takes my blood pressure before the shot. She recorded my blood pressure before my first shot and recorded it as normal. With each additional shot my blood pressure went up and up. After the 4th shot she refused to give me anymore injections until I brought her a note from my doctor. I made an appointment with my GP who wasn't as concerned about the blood pressure as he was by my B12 levels so I started going to my doctor's office for my shots. Not nearly as convenient as just walking down the hall to the nurse's office. My blood pressure is still a little high but down from where it was during the loading phase.


so it was high when it was measured when you were having a shot but was it being measured at other times to see if it was high when you weren't getting a shot.

exercise will raise blood pressure because it pushes up the amount of oxygen needed by muscles so the body responds by pumping the blood around faster - which results in a raised blood pressure - blood pressure also tends to be lower in the morning when you have been rested during the night - and of itself high blood pressure isn't a problem - though it can be indicative of other problems (eg if it is caused by buildups of deposits that make your blood cells narrower).

to know if your blood pressure was consistently high you would need to be monitoring the blood pressure throughout the day and over a period of time. diagnosis of hypertension via three elevated readings is a bit of a problematic way of providing a diagnosis - particularly when white coat syndrome is taken into account. If the pace at which you had got to the nurses office had changed that could have resulted in blood pressure going up for quite natural reasons.

B12 affects the autonomic systems as well as production of red blood cells ... and a lot of other processes. So it could be that signals to your autonomic system started to come through a lot stronger so your brain was more aware of needs for extra oxygen and responding to this more than it had been before ... and it takes the brain a while to respond to nerve signals coming through stronger - also a potential reason why aches and pains can be worse when receiving loading shots.

that's all just a possible mechanism but there is no way of guaranteeing that it applied to you.

but back to raised blood pressure can be a useful indicator of other underlying conditions but isn't a problem in itself - but that somehow seems to have got lost in recent times.


Yes, it happened to me until I took enough potassium and folate (methylfolate) to support the building of new cells caused by the B12 injections (methylcobalamin needed for my genetics). Potassium is used up quickly when B12 begins repair. It can be dangerous when it drops too low. I feel well when my blood potassium (on normal blood count on blood test form) is 4.5. Even at 4.2 I get high blood pressure and a few palpitations. Having enough folate is important too. It works with the potassium to reduce water retention and blood pressure. I lost a huge amount of water weight when I got things right. Took a year to get things going and I still have lots of repair to do.

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Hello All! I left a post about the very same issue a few weeks back. My blood pressure started rising very shortly after starting my loading doses. It was going up in marked increments. I questioned my oncologist/hematologist and he did not think it was related. However I went online and checked and Mayo Clinic does list as a side affect of B-12; especially folks who are predisposed to hypertension. (Before diagnosis of PA my BP had gotten a lot lower than normal and I attributed to fact I seemed to be losing a great deal of weight not thru diet but thought it was attributed to all the hiking and XCSkiing I was doing. I was on low dose of a BP med and since it got so low I quit taking the meds and did fine for almost 2 years. ). Well NOW my BP was going up in marked increments as weeks of iron infusion and B12 have gone by. My weight remained stable. Doctors said not to worry as I'm prbably just anxious. Ten days ago my BP went extremely high. Now, My oncologist got VERY CONCERNED and asked if my internist was aware. I made emergency appointment with internist and he was also concerned. As my body is building blood supply back up and I'm getting back to as normal as I can hope for, it's evidently using up potassium and I'm retaining fluid. He put me on The lowest dose BP meds (lisinopril-HCTZ - 10-12.5 Mg) and I started peeing volumes and by next morning my BP was back to normal. I'm seeing him in 3 days for another check by internist and he is doing blood check on potassium and sodium levels. Meanwhile I'm watching sodium intake and will stay on BP meds. What I found interesting since being diagnosed with PA and loading doses started I was drinking tons of water but my urine volume was DOWN. I also mentioned this to both doctors and they didn't seem concerned so I dropped the issue. They seemed more focused on my PA treatment... I think with all the other stuff going on with me they didn't take me seriously. Bottom line, I'm not a whacko or hypochondriac and we all know our own bodies best.


Very interesting, CH52, and glad you're okay now! I had the peeing volumes too when I upped the potassium & folate. I'll keep an eye on things even more now, given your experience. Low potassium is so dangerous for us and doctors don't even mention it when we start B12 injections..


I want to thank all of you for your responses. I think I will try taking folate and potassium. i think I read somewhere that your body needs a lot of magnesium, potassium, and calcium to process B12. I had been trying to eat a banana and some yogurt every day. Maybe I'll try supplements. I have to say, I feel so much better since I started receiving B12 shots.

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yes, my BP has become higher with B12 after being very low all my life. GP not worried, though and it is still only slightly high. I had numb and tingling toes for 12 years before I was diagnosed with B12d and was also given shoe inserts by a podiatrist because I could hardly walk. But stay optimistic... my toes are almost normal (well, almost almost) after 9 months injections (SI weekly now, plus extra folate). If my toes start to tingle or go numb I know it is time for an injection (I need more if stressed or doing physical exercise but I try to space them). So maybe your feet will recover, too.

Good luck - the injections make such a difference, I'm sure you will continue to feel better. I think you need supplements as well as a good diet because you will be using vitamins and minerals faster when repairing cells with your new B12 (that's my belief, anyway) and it isn't possible to eat the amount you need.

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Thank you for replying to my question. The only other issue I was having from my B12 shots was trouble sleeping the first night or two after receiving my monthly shot. I found that taking a magnesium supplement or taking a long soak in the tub with Epsom salts before I go to sleep fixed that problem. I just started taking a potassium supplement this week but I haven't taken my blood pressure so I don't know if it will help with lowering my BP numbers.

I can't explain how much better I have felt since I started getting B12 shots. I have told all of my family and friends to get their B12 levels checked when they have their physical. I am now a crusader for B12 testing. From the moment I received my first shot I started feeling like myself again. I feel 20 years younger and my skin looks better also.

I think this condition is under diagnosed. My GP told me that in the 50s and 60s doctors handed out prescriptions for B12 like candy but because it was given to everyone without testing, the medical community drifted away from diagnosing B12 deficiency.


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