Methylmalonic Acid and Homocysteine Panel
The two most sensitive markers for confirming early B12 deficiency, often before blood counts shift.
Consider this test if:
- Fatigue, brain fog, numbness or tingling, weakness, or balance problems with a borderline B12 result
- Confirming whether a low-normal serum B12 reflects true deficiency
- Following a vegan or vegetarian diet, or taking metformin or acid-reducing medication long term
- Separating B12 deficiency from folate deficiency before starting treatment
- Monitoring response after starting B12 supplementation or injections
- HSA/FSA eligible
- Results delivered to your dashboard · Reviewed by a real clinician
- Drawn at a CLIA/CAP-accredited lab near you ·
Pre-test considerations
Fasting is generally recommended, since recent meals and B vitamin intake can shift homocysteine. If you take B12, folate, or B6 supplements or receive B12 injections, note the dose and timing, as supplementation lowers these metabolites and can mask a deficiency. Kidney impairment also raises both markers independent of B12 status.
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What this test is for
Methylmalonic acid (MMA) and homocysteine are metabolites that build up when vitamin B12 is functionally low, which makes them the most sensitive way to confirm a true deficiency. MMA rises specifically when B12 is lacking, while homocysteine rises with B12, folate, or B6 shortfall, so the pair together points more precisely at the cause. This panel is most useful when a standard serum B12 sits in the gray zone and the clinical picture (fatigue, brain fog, numbness or tingling, weakness, poor balance, or glossitis) suggests deficiency despite a borderline number.
Running both markers separates B12 deficiency from folate deficiency: high MMA with high homocysteine points to B12, while normal MMA with high homocysteine points toward folate. The individual Homocysteine and MMA tests cover each marker alone, but this panel is the standard combination for working up suspected B12 deficiency.
Biomarkers tested
Includes 2 biomarkers
Homocysteine is an amino acid byproduct of protein metabolism, and B vitamins (B12, B6, folate) clear it from the blood before it builds up. When those vitamins run low, homocysteine rises, which is why it's a useful cross-check on B12 and folate status, especially in vegetarians, vegans, or anyone on metformin or acid-reducing medication. Elevated levels are also an independent marker of cardiovascular and cognitive risk, so it's worth tracking as a baseline alongside ApoB and Lp(a), or investigating if you're dealing with fatigue, brain fog, or numbness and tingling.
- Specimen
- Serum or plasma
- Measures
- Substance concentration
Methylmalonic acid builds up in your blood when cells lack the B12 they need to run a key metabolic reaction, making it a sharper, more specific marker of B12 status than serum B12 itself. It rises early, often before B12 drops out of normal range, so it catches functional deficiency that a standard B12 test can miss. Useful as a baseline if you're vegan, on metformin, or over 50 (all common depletion risks), and equally useful for investigating fatigue, numbness or tingling, poor balance, memory fog, or unexplained weakness.
- Specimen
- Serum or plasma
- Measures
- Substance concentration
What to expect
- 1 Book instantly
Click, book, done. Choose a convenient lab location near you. Transparent, up-front pricing.
- 2 Quick lab visit
Testing to fit your busy schedule, usually 15 minutes or less. Walk-in and appointments available.
- 3 Fast, dashboard-delivered results
Your results post straight to your dashboard as soon as the lab completes them.
- 4 Expert guidance
Included with Mito membership. A clinician reviews your results and your personalized action plan follows, with clear next steps.
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Frequently asked questions
View all FAQsHow does pricing work?
Every test shows the member price next to the standard non-member price, so you can see what membership saves you. The member price is our cost — covering the lab and what it takes to run the service — never a profit on the test itself; Mito makes its money on the $9 membership, not on marking up your tests. Membership is $9/mo, and you still pay the lab’s order fee. Prices are itemized before you pay, with no hidden fees.
Where do I get tested?
Choose a partner lab (Quest, Labcorp, or BioReference) at checkout. If your cart spans multiple tests, we consolidate the whole order onto a single lab so you only make one visit.
Is this eligible for HSA/FSA?
Yes. This test is HSA/FSA eligible, and you can pay with your HSA/FSA card at checkout.
When will I get my results?
Your results post to your dashboard once your lab completes them, then a clinician reviews them and your full analysis and personalized action plan (with clear next steps) follow. Turnaround varies by test: specialty assays and at-home kits take longer, and each test shows its expected turnaround before you buy.
Do I need a doctor’s order?
No. Mito provides the lab order for you, so you can book and get tested without a separate doctor visit.
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