B12 is making me tired all the time

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I have had tests four times for b12 after my sister was diagnosed with pernicious anemia. The results are varied between 160-200 at the moment it's 160. Had an injection yesterday and taking b12 tablets after that. How long will it take for the injection to work? Why would it drop from 180- 160 in a few days ?

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  • Posted

    Hi Vicky,

    I'm not a medically trained person but have had Pernicious Anaemia (a form of B12 Deficiency) for 45 years.

    Sadly the tests for serum B12 are not that reliable nor those for intrinsic factor and gastric parietal cell antibodies which presumably you have been tested for as there is a family connection to P.A. with your sister.

    How long have you been B12 deficient and what neurological symptoms do you have?

    What is your schedule for B12 injections?  If they are "every other day until there is no further improvement" in accordance with the B.N.F. guidelines there should be no need to supplement with tablets.

    As to how long for the injection to work you may find some symptoms improve immediately whereas others may appear to get worse before the get better - this could be due to the B12 starting work repairing the damage done to your nervous system by the deficiency..  There is no set time scale as we are all different and at different stages.

    Apart from the P.A. connection with your sister do you have any idea why you are B12 deficient?  There are so many freasons - too numerous to post here but I can send them to you by private message if you wish

    Do you know what your iron and Folate levels are as these two work togther with the B12 to form red blood cells?

    I wish you well

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    • Posted

      Hello Clive,

      Thank you for your response. My B12 been low for a around 3 months that I know off the only other low vitamin is d.

      I've had one injection and going on the B12 tablets i must admit I do feel worse for the injection.

      I have had these symptoms for a while but due to having anxiety they always put it down to that. I thought I was getting dementia the memory loss and confusion is embarrassing and I'm sleeping too much, tired as soon as I get up and out of breath.

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    • Posted

      Some of the symptoms of a Vitamin D deficiency are much the same as for B12 so it could be a combination of both.

      Are you prescribed anything for the low Vitamin D?  Improvement in that may take 2 - 3 months depending on its severity and strength of pills.

      Is you doctor just giving you one B12 injection and no more and did he/she prescribe the tablets, or are you doing that yourself?

      A deficiency in Vitamin B12 may cause any or all of the following symptoms - have a look and see if any others (I've not highlighted) apply to you.:


      Fatigue, sometimes severe

      Feeling of heaviness in arms, legs and head

      Muscle weakness

      Depression and despondency

      Easy bruising

      Sleep disturbances and insomnia

      Hormonal imbalances

      Elevated liver enzymes

      Diarrhoea, constipation or other digestive woes such as nausea, vomiting, loss of appetite and/or bloating

      Red, swollen tongue

      Bleeding gums

      Pale skin

      Brain fog,” problems concentrating, memory loss

      Shortness of breath on even mild exertion

      Numbness or tingling in extremities (neuropathy in severe cases)

      Headaches and migraines

      Ataxia (lack of balance, may affect gait)

      Dizziness and light-headedness

      White spots on the skin of the forearm (may be misdiagnosed as Vitiligo)

      Irritability and extreme mood swings

      Tachycardia, skipped heart beats, irregular heart rhythm

      Eye twitches and tics

      Irregular periods, heavy bleeding, infertility

      Decrease or disappearance of normal reflex responses

      Some people report pain in their ring finger and palm

      Causes of a Vitamin B12 Deficiency

      The following are all potential causes of a B12 deficiency:

      Alcohol consumption


      Vegan or vegetarian lifestyle

      Excessive junk food consumption

      Digestive diseases and conditions which block absorption (Celiac, Crohn’s, IBS, malabsorption, etc.)

      Removal or resectioning of the small bowel

      Use of antacids and prescription drugs used to treat ulcers

      Gastric bypass surgery 

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    • Posted

      Hi again Vicky,

      Well that suggests to me that the doctor doesn't think that you have an absorption problem via your siomach, gave you the one injection to boost your B12 level and given you "maintenance" doses of B12 and D so hopefully you are now on the right track to recovery.

      As I said before symptoms of Vitamin D deficiency may take a while to improve depending on its severity and dosage of the tablets.  Try to get out into the sunshine for twenty minutes a day now spring is here.

      As for a B12 deficiency again improvement of some symptoms can happen quickly but any damage caused to your nervous system may take longer - depending on its extent.

      I hope you stsrt to feel better soon.

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  • Posted

    Hi, I don't understand why your dr wouldn't follow the NICE guidelines and give you the full 6 loading injections. You will most probably feel tired after the first few- take it easy on yourself. I think if you know it is going to happen then you are prepared. I'm sure you thought it was odd being tired. As Clive said, other symptoms may get worse before they get better. Unless you are vegetarian or vegan, it is highly unlikely to be diet deficiency- therefore you MUST have the injections- the tablets WILL NOT work.

    You really should do lots of reading and research. Your dr, unless unusual- will not know how to treat you. Please get informed and be prepared to push for the right treatment.

    Make yourself some nettle tea- put some rosemary in for memory and concentration and perhaps some lemon balm or lemon grass which will give a lovely flavour - and will help with mood. Nettles amazing things. (I'm now a student herbalist after all my problems with NHS). A heaped teaspoon of mixture- add boiling water and leave 10 mins or so and drink hot or cold. 2-3xs a day. Won't cause any problems and could be picked from your garden. Enjoy.

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