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    What causes increased heart rate after taking vitamin B12 shot?

Posted on Wed, 16 Aug 2017 in Hypertension and Heart Disease
Question: I have taken my first b12 shot today... I feel my heart beat has become faster... Is it a thing to worry????
Answered by Dr. Shuba Hariprasad 2 hours later
Brief Answer:
Most likely nothing to worry, pls get back with clarifications

Detailed Answer:
Thank you for your query.
I'm Dr. Shuba Hariprasad and will be answering your query today.
Would you clarify a few things for me, please?
*how old are you?
*do you have any other medical issues or take any other medications?
* what is your regular heart rate and how much is it now?
*do you have any other symptoms like chest pain, breathing difficulty, giddiness, unexplained sweating, fever, rash, any swelling at the site of injection, trouble lying down?

Vitamin B12 deficiency can cause fast heart rate which can be dangerous if not treated.
A shot of the same does not result in fast heart rate unless the shot was not gives right or if you are allergic to it.

Based on your description, there is nothing to worry about especially if you are comfortable otherwise.
Please get back to me with the above clarifications so that I may help you better.

Dr. Shuba Hariprasad

Above answer was peer-reviewed by : Dr. Prasad
Follow up: Dr. Shuba Hariprasad 2 hours later
I had giddiness and my pulse rate was 80.... I could feel my heart beat.... I had stomach pain.. Now my pulse rate is 75.... Stomach pain still persists...little tired.... Feeling light

I have thyroid and I take thryronorm 50 mcg...apart from that nothing else

I am 29 years old...
Answered by Dr. Shuba Hariprasad 18 minutes later
Brief Answer:
If persists, see your doctor, check blood pressure, sugar & thyroid

Detailed Answer:
Thank you for the follow up and clarifications.
A pulse rate of 75 to 80 is absolutely normal.

Palpitations (feeling of heart beating) with giddiness & stomach pain is not normal. It could be due to anxiety or that you haven't had much to eat. Side effects of vitamin B12 can also result in your symptoms.

I recommend :
-Have something bland to eat.
-sleep for a while

If you still have these symptoms
-inform your doctor right away
-see your doctor to check blood sugar and blood pressure levels
-have an electrocardiogram and echocardiogram
-check TSH levels if it has been more than 6 weeks from your last thyroid test.

If you feel better, then it's OK.

If your symptoms worsen or breathing difficulty, chest pain develop,cisit the emergency and don't drive.
This is not to scare you but for you to be aware and know what to do.

Hope I've helped.
Please let me know if you have any further queries.

Wish you good health.
Dr. Shuba Hariprasad

Above answer was peer-reviewed by : Dr. Yogesh D
Answered by
Dr. Shuba Hariprasad

General & Family Physician

Practicing since :2002

Answered : 1087 Questions


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