Hi. I have recently been diagnosed with vitamin b12 deficiency. My last test was:
Vitamin B12 = 140 pg/mL (200 -1000)
My PCP prescribed me cyanocobalamin 1000 mCg/mL injectable solution weekly for 4 weeks then monthly.
I got my first shot today and I was wondering how long it will take to see any improvement.
Thanks.
It varies Depends on your symptoms and how long you've been deficient for.Sone pick uo within days or weeks
Others can get worse
before better.
Main thing is you are getting treatment.
Was your folate iron, vit D also checked along with fbc? (Full blood count)
Most take a multivit to support healing.
Hope you feel the benefit soon.
Ni Nackapan. Thanks for your reply.
My vitamin D was also low - Vitamin D Total = 20.5 ng/mL (Reference range: 30 - 100)
I am taking supplements weekly - ergocalciferol (vitamin D2) 50,000 intl units (1.25 mg) oral capsule
I did not have folate tests 
and I am not taking multivitamins either.
Have a nice weekend!
Some notice results immediately, and others see no improvement for a while.
Personally, the injections immediately made me regain feeling in my hands and feet, but not fully. It also cleared up the brain fog and apathy I was feeling. The improvement of my memory loss was most notable. I previously needed someone to sit in the car with me and direct me on where to go, because I couldn't remember where anything was.
This process of healing manifested as shooting, burning pains. I know I'm healing because I feel pain and then regain some sensation.
So it depends on what you were experiencing to begin with.
What's important is your red blood cells. When those die and are recreated by the body, if you have sufficient b12, you'll create new, healthy ones.
Ones who can do their jobs and aren't sick. This process takes months, which is why healing is so slow.
Thanks, Sammyo23. My main problems are extreme fatigue and muscle weakness. Also, I have difficulty focusing. I had to skip the semester at the university because I wasn´t able to study.
I try to be patient but I really want to have a normal day and feel energized again.
I have exactly the same symptoms as you. I have been taking b12 injections every three months. I don't really feel any better. The last one left bad bruising on injection site. It's still the same after 6 days. Felt really tired for first two days. That's the first time I have had a reaction like that. Although, I have a kidney disorder, so this might contribute. I drink beetroot juice every day. Small glass full. This helps give me energy.
Hi, Natural1970. The main difference I notice since the shot is that I have more appetite. In the last months, I was never hungry, I had to obligate myself to eat. I felt weird with the loss of appetite because I was a person who really enjoying food and eating.
Thanks for the recommendation of beetroot juice. Hope you feel better soon 
after 15 years I,m still waiting to feel better not too sure it will ever happen now.Others feel a buzz immediately or with in a couple of days
Good luck
I noticed a decrease in pain within hours. And I'm usually insomniac that first night.
I noticed a difference in a day or two, the first time I had an injection. After that, it would take 12 hours. I still (after a year) need to take a B12 injection once a week. Otherwise I start suffering from depression, anxiety and sleepiness.
Hi Marla. Thanks for sharing your experience.
In the lasts months, I was very emotional and sensitive, also I had a high level of anxiety. My sleepiness during the days comes and goes, this last week was very bad. Some days I slept 10 hours and woke up feeling extremely tired, others days I slept 9 hours, and I had to nap for 90 minutes. I felt exhausted. In the past, I was OK with only 7 hours of sleep.
I had depression some years ago and I know how hard it is. Luckily this time I have more tools to do as much I can for my mental health, but it is very difficult to live in a body that tricks you.
It´s like baby steps. And we need to learn to feel and listen to our bodies.
I feel like it depends on how low your B12 is and the severity of symptoms. After my first injection, I felt significant improvement the following day without feeling worse. On another occasion after a 3 month lapse in treatment, it took 3 days to notice improvement but I had to go to bed the evening I received that injection—a pattern that continued for several weeks. You may feel worse before you feel better. Don’t be discouraged if b12 numbers climb, but you still feel bad. I panicked when this happened to me and thought that there was something else wrong with me until my neurologist explained that it takes the brain an entire year to heal after b12 is low. Though you may begin to feel better, recovery can be a slow process. Best of luck on your healing journey.
Thank you for sharing your experience. Good luck for you too
As others have said, it really depends on the individual. For me, they’re effective almost immediately/within 24 hours. Do note it’s really important not to miss your appointments as your B12 levels could drop further. I was 2 weeks late once because I had to self-isolate and it was the most torturous 2 weeks since I was diagnosed. I was sleeping all the time but feeling so exhausted and my memory just wasn’t working. Hope it’s worked quickly for you!
Hi, Moarny! I've fought so hard to get the prescription of Vit B12 that I think I would never miss a shot! I felt a little better in these last 3 days after the shot. I can´t wait to have my 2nd one to see more improvements. From the 3rd shot, I will have to inject myself. I asked to have a mini-training at my local hospital (I live in the US)
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