u/sunnydays7777

I got my first B12 shot (cyano) 3 days ago and haven’t noticed much of anything yet. Perhaps some more clear thinking the day of the shot. I gave it a couple of days and then re-started taking sublingual methycobalamin today.

Mainly I have been SO tired. That is one of my main symptoms, but I think it’s even worse since the shot. I don’t notice any obvious “wake-up” symptoms. Just so much fatigue. After taking doses of the sublingual methyl I felt a small boost in energy, short-lived.

Should I be feeling something after the shot if my symptoms are actually caused by B12? My levels have been borderline low (300 initial, then in 400s after oral supplementation) but I haven’t supplemented B12 in a month so I thought I would feel something.

I just met with a new Dr to discuss symptoms that I believe are related to B12 deficiency (300 level in baseline test a couple months ago, prior to oral supplements). She wanted to repeat my B12 test as well as test thyroid, etc.

I had booked my own B12 test one day earlier and hadn’t gotten the result yet, so I decided to go along with her test (run by a different lab). I have now gotten both results. My test showed 390 (this is within a month of supplementing). The Dr-ordered test shows 490. What gives?? That test is 100 points higher, one day later, and I did NOT supplement during the day between tests. Of course, the Dr now has said my B12 level looks normal. She has agreed to give me a round of once-monthly shots, which I know isn’t enough but at least I can have something to go on and see how I feel after one shot…

This seems crazy and makes me question how reliable any of these tests are. I feel so defeated.

I have an appointment in 3 weeks for a different PCP who supposedly has some experience with treating B12. I was hoping to get one sooner, but that was the best they could do. am hoping to get a prescription for injections. I plan to bring blood tests, list of symptoms, and a couple of the medical guideline literature in case I need back-up.

MY QUESTION: Is it generally better for me to keep taking sublingual until I can meet with her, or to take a break so as to feel more of the weight of the symptoms and in case she wants to do more blood tests? I’ve already gotten the following tests, which I will bring:

B12 - 301
Folate (serum) - 9.1
MMA - 102
Homocysteine - 6.2
Hemoglobin - 12.1 (female so not considered anemic)
MCV - 99.7
Ferritin - 153 (post-infusion; previously was 10)

History: On-and-off anemic with low ferritin for years, especially during heavy bleeding several years ago (bleeding now resolved). Was told years ago I was low in B12 with anemia type consistent with that type of deficiency, but didn’t understand that I needed to stay on top of it. I have taken a b complex in recent years and was tested for B12 a couple times coming in around 450-500.

Recent history: All sorts of horrible symptoms, culminating in significant worsening in April after a very stressful time. I couldn’t function, had to stop working, and needed lots of naps, with horrible insomnia at night. My worst symptoms included cognitive and memory issues, dropping things, dizziness, dypsnea, anxiety, digestive issues, constant PVCs/palpitations. Given blood test results from January and April (below), my GI MD prescribed a round of iron infusions, a series of 5, once a week (started early May through present). She also suggested B12 oral supplements. I’ve been taking 1,000 methylcobalamin sublingual most days, plus B complex.

Now: Some symptoms now better (PVCs, digestive issues, anxiety), but others continue and I have had extreme fatigue.

Just got results from a blood test done this week (after 4 of 5 iron infusions). To my eyes, my CBC results look WORSE despite my ferritin increasing, and potentially trending to B12 anemia type markers. I’ll get my “official” post-infusion tests done in a couple of weeks, but want to be prepared if I need to push for B12 injections or hematologist referral. Would love a gut check. Thank you, already reading this sub has been so helpful!

Jan 2026:
RBC: 4.03 (Low; range: 4.2-5.4)
HGB: 12.7 (Range: 12-16)
HCT: 37.8 (Range: 37-47)
MCV: 93.8 (Range: 81-99)
MCH: 31.5 (High, range 27-31)
MCHC: 33.6 (Range: 33-37)
RDW: 12.2 (Range: 11.5-14.5)
MPV: 10.8 (High, range 7.4-10.4)
Ferritin: 10 (Range: 6.24-137)

April 2026
B12: 301 (range: 200-1100)
Folate: 9.1 (range >5.4)
MMA: 102 (range 55-335)
Homocysteine: 6.2 (range <11)
Unfortunately no CBC done at this time

Iron Infusions started early May, once / week; along with Sublingual Methylcobalamin (1000mg) and B complex

June 2026 (this week): (Confusing that reference ranges now look different, perhaps because I used a different lab)
RBC: 3.86 (lower than Jan test but now says normal with range of 3.8-5.1)
HGB: 12.1 (lower than Jan; Range: 11.7-15.5)
HCT: 38.5 (Range: 35.9-46.0)
MCV: 99.7 (Higher than Jan; Range: 81.4-101.7)
MCH: 31.3 (Range: 27-33)
MCHC: 31.4 (Low; range: 31.6-35.4)
RDW: 12.7 (Higher than Jan, Range: 11-15)
MPV: 10.6 (now says normal, with range 7.5-12.5)
Ferritin: 153 (Range: 16-232)
B12: 463 (I know this means nothing now as I’ve been supplementing)

I had my first (of a series of 5) venefer infusion 5 days ago. (Ferritin: 10, not officially anemic with Hg 12.7, but low red blood cell count.)

First two days I felt an energy boost and almost no side effects except a small headache. I’m not sure if I overdid it those days (I finally had a bit of energy!) or if the side effects then kicked in. For the last 3 days I have been SO tired and last night I started having some abdominal bloating, chest tightness, and skipped heartbeats (which is something I get regularly, likely from the low iron - but it was amped up a bit). I feel pretty rotten and have just been lying in bed most of the day.

I’m wondering, is this normal side effects of venefer? Or could it possibly be hypophosphatemia (which I’m paranoid about!). Or did my body use up the initial dose of iron and now is feeling depleted again? If anyone has advice / support, I would be very appreciative.