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ForumsLab Results & BiomarkersVitamin B12 monitoring — what worked for you?

Vitamin B12 monitoring — what worked for you?

bri_stats Fri, Sep 26, 2025 at 8:27 AM 9 replies 1,237 viewsPage 1 of 2
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bri_stats
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May 2024
Seattle, WA
Sep 26, 2025 at 8:27 AM#1

Six months of eating roughly 1,100 calories a day and my ferritin has halved, which I did not connect to the intake until somebody pointed it out.

Cheap and worth having: ferritin, B12, vitamin D. Everything else on the deficiency list is adequately covered by a standard multivitamin at ordinary doses.

What I am trying to establish is which deficiencies actually show up when intake drops this far, and which are worth testing rather than supplementing blind.

Numbers rather than impressions, if you have them.

46 16sarah_nash92, FitDadDave, RunnerRach and 43 others
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PharmacoVig_BOS
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Feb 2024
Boston, MA
Sep 26, 2025 at 8:38 AM#2
bri_stats said:
Six months of eating roughly 1,100 calories a day and my ferritin has halved, which I did not connect to the intake until somebody pointed it out.

Iron studies on micronutrients — important especially for women:

MarkerBaselineMonth 6After Supplementation
Ferritin702355
Iron1006083
TIBC335405335
Transferrin Sat33%15%26%

My ferritin cratered at month 6 from reduced dietary intake. Iron bisglycinate 36mg with vitamin C brought it back up. Don't wait for anemia symptoms — test proactively.

Last edited: Sep 26, 2025 at 11:38 AM
45 15Dr.GutHealth, amsterdam_pete, LondonLisa and 42 others
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JakeBK_lifts
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Brooklyn, NY
Sep 26, 2025 at 8:49 AM#3
PharmacoVig_BOS said:
Iron studies on micronutrients — important especially for women: Marker Baseline Month 6 After Supplementation Ferritin 70 23 55 Iron 100 60 83 TIBC…

Vitamin and mineral labs to check while on micronutrients — my doctor orders these quarterly:

  • B12: Can drop due to reduced GI absorption. Mine went from 650 to 380 — now supplementing.
  • Iron/Ferritin: Reduced food intake = reduced iron. Ferritin dropped from 71 to 28. Supplementing.
  • Vitamin D: Was already low (18 ng/mL), now taking 5000 IU daily.
  • Folate: Stable, no issues.
  • Zinc: Slightly low, added a multivitamin with zinc.

Nutritional deficiencies are a real risk when you're eating significantly less. Don't skip your labs!

44 14LabKate, kate.chem, DataDave and 41 others
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mel_PDX
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Dec 2024
Portland, OR
Sep 26, 2025 at 9:00 AM#4
bri_stats said:
Six months of eating roughly 1,100 calories a day and my ferritin has halved, which I did not connect to the intake until somebody pointed it out.

Can confirm. Same sequence, different timescale.

43 13BiostatsBrad, PeptideSynthNJ, Dr.KarenChen and 40 others
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sophie_paris
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Paris, FR
Sep 26, 2025 at 9:59 AM#5

Clinical perspective, offered as context rather than as advice.

Vitamin D levels and micronutrients: an often-overlooked connection. Obese individuals store vitamin D in adipose tissue, making it less bioavailable. As you lose fat, vitamin D can actually increase WITHOUT supplementation.

My trajectory: Baseline 18 ng/mL → Month 6 (with supplement) 42 ng/mL → Month 12 48 ng/mL. Target is 40-60 ng/mL. Adequate vitamin D supports immune function, bone health, and mood — all relevant during weight loss.

42 12BethLabQueen, ChrisMacros, KetoKyle and 39 others
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