Evaluating low vitamin D or B12 starts with checking whether a 25(OH)D or B12 blood test is needed and whether oral doses, weekly nasal spray, or injections match the cause.

A specific doctor reads your whole case and answers with a written plan and a Human Signature (a short video or voice note recorded live for you), so no form gets approved in bulk. We believe AI is a tool for doctors and the doctor is in charge of every case. Because health problems have nuance and only an expert knows when AI errs, our AI works behind the scenes like a chief resident to gather history and organize your case, never giving medical advice by itself.

You can message the same doctor time after time in the same chat, however long in between, to build trust, try treatments together, and track progress, such as comparing a new B12 result against your baseline on metformin (the label advises a check every 2 to 3 years) or adjusting vitamin D. FutureClinic sells no medicine, your doctor earns nothing extra for any prescription or test, you never have to stay subscribed to keep your medicine, and they can prescribe any brand or generic medicine to the pharmacy you choose if your doctor decides it's right for you. That same doctor can help with other problems in their specialty, and every FutureClinic doctor you see works from one medical record.

Which blood tests check vitamin D and B12?

In its June 2024 vitamin D guideline (abstract), the Endocrine Society suggests against routine 25-hydroxyvitamin D, or 25(OH)D, screening or follow-up dose testing in generally healthy adults, pregnancy, obesity, or dark complexion, absent an indication like hypocalcemia (low blood calcium). The US Preventive Services Task Force (USPSTF) also found insufficient evidence to screen asymptomatic adults, noting assay variation and no consensus cutoff (per the National Academy of Medicine, 97.5% meet bone needs at 20 ng/mL, with deficiency risk below 12 to 20 ng/mL).

Untreated B12 (cobalamin) deficiency can harm blood cells and nerves, per the National Heart, Lung, and Blood Institute (NHLBI), which lists a blood count and B12 test (400 pg/mL or higher normal; 200 pg/mL or lower deficient). Under the UK's March 2024 NICE B12 guideline (NG239), first-line testing is total B12 or active B12 (used in pregnancy): total B12 below 180 pg/mL confirms deficiency, 180 to 350 pg/mL is indeterminate, and above 350 pg/mL makes deficiency unlikely. Indeterminate results with symptoms may prompt a methylmalonic acid (MMA) test, or anti-intrinsic factor antibodies for suspected pernicious anemia.

AI vitamin D and B12 treatment: what the doctor does with your results

Your doctor reviews supplements, diet, surgeries, and medicines by message (prior B12 supplements can raise levels without curing deficiency; combined birth control pills can lower total B12 without causing a deficiency). Per NHLBI and NICE, doctors check vegan diets, autoimmune conditions (pernicious anemia, celiac, thyroid disease, type 1 diabetes, vitiligo), bowel or pancreatic disease, gastritis, alcohol or nitrous oxide use, and bariatric or stomach surgery. On the metformin label, 7% of patients in 29-week trials saw normal B12 drop below normal, so B12 checks are advised every 2 to 3 years and blood counts yearly. Long-term acid blockers may impair absorption, per NICE and the omeprazole label (over 3 years).

For vitamin D (D3 or D2), the Endocrine Society suggests empiric supplementation without testing for ages 1 to 18, adults 75 and older, pregnancy, and high-risk prediabetes with lifestyle changes (the guideline says optimal doses remain unclear; prediabetes trial doses ranged from 842 to 7,543 IU a day, a weighted average of about 3,500 IU). Healthy adults under 75 should follow the recommended daily allowance of 600 IU up to age 70 and 800 IU over 70; for adults 50 and older who have a reason for vitamin D, the Society suggests a daily lower dose rather than intermittent high doses. Prescription 50,000 IU ergocalciferol capsules are labeled for hypoparathyroidism, vitamin D-resistant rickets, and familial hypophosphatemia, and contraindicated with high calcium, malabsorption, or toxicity (typically above 150 ng/mL per USPSTF).

For B12, a 2018 Cochrane review of three trials (153 people) found low-quality evidence that 1,000 to 2,000 mcg daily oral B12 raised levels similarly to or higher than shots at lower cost. NICE advises considering oral B12 for dietary or unknown causes without malabsorption, offering oral or injected B12 for medicine or nitrous oxide causes, and considering injections for other malabsorption (at least 1 mg daily if oral). Over-the-counter B12 should contain cyanocobalamin, methylcobalamin or adenosylcobalamin, and weekly Nascobal (500 mcg nasal spray) is labeled for maintenance in adults with pernicious anemia who are in remission after B12 injections and have no nervous system involvement. An in-person clinic suits patients needing lifelong intramuscular cyanocobalamin shots after total gastrectomy, complete terminal ileal resection, or pernicious anemia. For pernicious anemia, the US cyanocobalamin label says "The oral form is not dependable," and shots are usually given in an office or clinic.

How does messaging a doctor compare with an office visit?

New-patient appointments across 15 US metros averaged 31 days (23.5 in family medicine) in AMN Healthcare's 2025 survey, and an American Journal of Managed Care study found office visits averaged 121 minutes ($43 time cost in 2010 data). FutureClinic connects you by message with over 300 doctors in the US. They span more than 60 specialties, generalists and specialists alike. Every doctor is a physician with an MD, DO or MBBS degree, never a nurse practitioner or physician assistant. Real care takes hours, not seconds: replies typically come within a few hours, and almost always the same day or the next.

Before you pick how to get tested or treated, it helps to ask yourself: did you want a subscription program and its ongoing requirements, or did you simply want a physician of your own to check your levels and guide your care? If you want bundled monthly supplements or need in-office B12 shots, those routes are strong options, while FutureClinic gives you an expert doctor with nothing extra attached.