Together they would add more than half the cost of the panel again. Each is a good test asked at the right moment and a waste of money asked at the wrong one.
Vitamin D at ₡32,500, vitamin B12 at ₡22,000 and ferritin at ₡18,000 are among the dearest lines on a Costa Rican laboratory's list. Together they would add more than ₡72,500 to a panel — most of a second baseline.
The reason is mechanical rather than clinical: all three are immunoassays, antibody‑based tests that run in batches on costlier reagents. The cheap tests on your panel run on an automated chemistry analyser at a few hundred samples an hour. These do not.
None of the three is in our baseline. Each goes on when a specific question needs answering.
You would expect deficiency to be rare at nine degrees north. Studies in tropical countries keep finding otherwise, and the usual explanations are air‑conditioned indoor work, sun avoidance, clothing, higher skin pigmentation requiring longer exposure, and older age.
That said, the bigger argument is whether most people should be tested at all. Several national bodies and the US Preventive Services Task Force have concluded there is insufficient evidence to recommend screening symptom‑free adults, and some explicitly advise against routine testing. The counter‑argument is that supplementation is cheap and safe at ordinary doses, which makes testing first look like an expensive way to reach the same place.
Where testing genuinely helps: malabsorption, bone disease, long‑term steroid use, previous bariatric surgery, or an unexplained picture that is not adding up.
One practical note — what should be measured is 25‑hydroxy vitamin D. A test reporting the 1,25‑dihydroxy form is answering a different and much more specialised question, and is a common ordering error.
This is the one with the clearest case in a metabolic clinic. Metformin reduces B12 absorption, the effect grows with dose and duration, and major diabetes guidance recommends periodic monitoring in people taking it long term.
It matters because B12 deficiency can cause nerve damage that does not fully reverse, and its early symptoms — tiredness, pins and needles, poor concentration — are easy to attribute to the diabetes itself.
Two complications worth knowing:
So B12 is on our metformin addition list rather than the baseline — ordered because a specific medicine is being taken, which is exactly the right reason to order a test.
Ferritin reflects iron stores and is the best single test for iron deficiency. It has one large catch: it is also an acute phase reactant, so it rises with inflammation, infection, liver disease and obesity.
That means an iron‑deficient person with inflammation can have a ferritin that reads normal. Where that is a real possibility, ferritin is interpreted alongside CRP, or with transferrin saturation added.
Ferritin can also be high for reasons that have nothing to do with iron overload — alcohol, fatty liver, metabolic syndrome. A raised ferritin in a metabolic clinic is more often fatty liver than haemochromatosis, but haemochromatosis is the one you must not miss.
It is ordered when the full blood count already suggests anaemia. That sequence is deliberate: the haemogram is ₡13,000 and in the baseline, and it tells you whether the ₡18,000 question is worth asking.
Each of these is a good test asked at the right moment and a waste of money asked at the wrong one. The question that keeps them off a standing panel is the same one that governs the whole list: would the result change what we do next? For most first visits, no. For a patient on metformin, or one whose haemogram shows anaemia, yes — and then it is ordered without hesitation.
Nothing here tells you whether to supplement anything. Dose, duration and whether a supplement is warranted at all depend on your results, your medicines and your history, and that is a conversation with a physician rather than a shelf in a pharmacy.
Every patient starts the same way: thirty minutes with a physician, then a full biomarker panel drawn at a laboratory near you. Whether any medicine follows is your doctor’s decision, made after reading your results with you.
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