Posting this because I spent way too long feeling awful and getting nowhere, and I want to save someone else the same struggle.

**Quick background:** I'm a lifelong lacto-vegetarian (no meat, fish, or eggs, but dairy is fine), which already put me at higher risk for B12 deficiency. When my levels came back low, I did what everyone tells you to do — oral supplements, then B12 injections when that didn't work. Neither one moved the needle for me. Here's what was actually going on, and what finally worked.

**Why the "standard" treatments didn't work for me**

**Two Oral Methylcobalamin B12 Supplements (combined 800 mcg) — no improvement.** Turns out I had mild chronic gastritis, which I only found out about after a full GI workup with a comprehensive colonoscopy and endoscopy. If your gut can't absorb it properly, it doesn't matter how many supplements you swallow.

**B12 IM injections — also no improvement.** This one surprised me. The injections I was given were cyanocobalamin, the synthetic form. After digging into my own genetics, I found out I carry the MTHFR A1298C mutation (heterozygous; C677T negative — for anyone who wants the specific test, it's Quest Diagnostics' "Methylenetetrahydrofolate Reductase (MTHFR), DNA Mutation Analysis," test code 17911). For people with certain MTHFR variants, the body reportedly has a harder time converting synthetic cyanocobalamin into the active forms it can actually use. That may well have been my problem.  
ADDED: The injections revealed something too. Monthly cyanocobalamin only got my B12 to 187 → 237, and twice-weekly reached 445 before falling back to 335-372 when frequency dropped. So even with the gut bypassed, monthly dosing couldn't hold a level — because cyanocobalamin has poor tissue retention and clears quickly.   
I discussed switching to Methylcobalamin injections with the doctor, the doctor agreed but here in California, there was a commercial shortage and methylcobalamin IM was not available. California state legislation also prevented out-of-state pharmacies from shipping methylcobalamin IM to California.

So between the gut absorption issue and possibly the wrong form of B12, I was doing "everything right" on paper and still not getting anywhere.

**What actually worked: sublingual B12, bypassing my gut entirely**

I switched to a **sublingual liquid B12** that skips digestion altogether and absorbs through the tissue under the tongue. Specifically, I used **Pure Therapro Rx BioActive B12 Full-Spectrum Liquid, 5000mcg**, (found on [Amazon](https://www.amazon.com/Pure-Therapro-Rx-BioActive-Full-Spectrum/dp/B07Y42SD1F/ref=sr_1_1_sspa?crid=3ADMUYSREXG3N&dib=eyJ2IjoiMSJ9.fYlt_0OR0LLTSGes3-kdxJHDwytMEGVsVLsZ6rl-usc19AZ5hWO6oA5Qu9R5eMWJigrV-N7_jk3y2JBSPbYazSJ2S3BA4leO9r3Hrk17f4XYKbrEg_69QdsrhfamZk06NQQ-dmjl8Snbov6tTuOmpC8ojjymgkGOsqOEk3BGrBdeXsEvuZnlbm0LnL7VYl0wEJLgQ7wsPHmOGDNtg799rDwBD_3z0Nqed8Nw9fOWQmj359WlojLlysZyHu_QHM4soIYvEF_k5GMc6PQCrKDHcoBdCSYf5YYzckPbyKsYxIo.nMkeLuO9T6FhW4woJGlhrk1Zs6ZEJPjAnTGR_dEAfIg&dib_tag=se&keywords=Pure%2BTherapro%2BRx%2BBioActive%2BB12%2BFull-Spectrum%2BLiquid%2C%2B5000mcg&nsdOptOutParam=true&qid=1789015639&rdc=1&sprefix=pure%2Btherapro%2Brx%2Bbioactive%2Bb12%2Bfull-spectrum%2Bliquid%2C%2B5000mcg%2Caps%2C151&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1)

) which combines three active forms in one dose:



* 2500 mcg MecobalActive® Methylcobalamin
* 1500 mcg Adenosylcobalamin
* 1000 mcg Hydroxocobalamin

Using multiple bioactive forms rather than just cyanocobalamin was the key difference for me.

**My protocol:**

* First thing in the morning, empty stomach, *before* brushing teeth or doing any mouth hygiene
* Held the liquid under my tongue as long as I possibly could, letting it dissolve with saliva
* Swallowed once I couldn't hold it any longer
* No food, water, toothpaste, or mouthwash for 20 minutes after

**Result:** Full B12 saturation in about 6 weeks. It genuinely felt like night and day compared to months of injections and pills doing nothing.

**Lessons learned, for anyone in the same boat**

1. **Advocate for yourself.** If a doctor brushes off your symptoms or won't explain the "why" behind a treatment, find one who will. You know your body better than a 10-minute appointment allows them to.
2. **You get very little time in front of a doctor — use it well.** I put together a longitudinal matrix tracking my labs over time so they could see the trend at a glance, printed out a list of specific questions ahead of time, and used Superpower AI to help translate my situation into the kind of clinical language that gets taken seriously in a specialist's office. I even emailed them a copy in advance of the office visit. Walking in prepared changed how those appointments went. **See attached image of a longitudinal matrix and medical summary.**
3. **"Standard" treatment doesn't work for everyone, and there's usually a reason.** Absorption issues and genetic variants like MTHFR can make the textbook approach fail even when you're doing it correctly. ***If something isn't working, that's a clue to dig deeper, not a sign to give up.***
4. **Consider tools built for exactly this.** I signed up for Superpower ([Superpower](https://superpower.com/) ) to help me actually understand what was going on with my own labs and history, draft medical summaries that spoke the doctor's language, and research which supplements or prescriptions made sense for my situation. Having that on hand made a real difference in how prepared (and confident) I felt walking into appointments.

**Standard disclaimer**

I'm not a doctor, and what worked for me won't necessarily be right for you — B12 deficiency can have a lot of different root causes (pernicious anemia, absorption issues, diet, genetics, medications, etc.), and "just take sublingual B12" isn't a universal fix. If you're struggling with this, please work with a doctor (or find one who'll actually work *with* you) and consider asking about MTHFR testing, a GI workup, rheumatology workup, hematology workup, etc. if oral or injectable B12 isn't helping.

Please share on what else should I consider. Happy to answer questions if anyone's dealing with something similar!

How I Finally Fixed My B12 Deficiency After Injections AND Oral Supplements Failed (MTHFR + Absorption Issue)