All Conditions
Condition Guide

Vitamin & Mineral Deficiency

Vitamin and mineral deficiencies are surprisingly common, even in well-nourished populations. A simple blood panel can identify deficiencies that explain fatigue, hair loss, bone pain and other symptoms.1

Written by Suman Konda, Clinical Pharmacist · Based on peer-reviewed sources · Editorial policy · Not medical advice

Last reviewed and updated: · How we check our content

What vitamin deficiency is

Advertisement

Vitamin and mineral deficiencies are surprisingly common, even in well-nourished populations — and a simple blood panel can identify deficiencies that explain fatigue, hair loss, bone pain and other non-specific symptoms. The most prevalent is vitamin D deficiency, estimated to affect around 40% of people globally.

The key vitamins measured when deficiency is suspected are vitamin D (25-hydroxyvitamin D), B12, folate, plus iron (via ferritin), magnesium, calcium, zinc and vitamin A — each with its own pattern of symptoms and risk groups.1

Vitamin deficiency: myths vs facts

Supplement marketing has muddied the waters. Here is what the evidence says:

MYTH If you eat well, you cannot be deficient.

FACT Vitamin D deficiency affects an estimated 40% of people globally, and very few foods naturally contain significant vitamin D. B12 deficiency takes 3–5 years of inadequate intake to develop because the body stores large reserves — diet quality today does not reflect stores.1

MYTH More vitamins are always better.

FACT Fat-soluble vitamins (A, D, E, K) accumulate in liver and fat — vitamin A toxicity causes raised intracranial pressure, liver damage and birth defects, and high-dose B6 causes peripheral neuropathy. More is not better; enough is.

MYTH Vegetarians get enough B12 from plant foods.

FACT B12 is found almost exclusively in animal products. Deficiency is particularly common in vegetarians, vegans and the elderly — and metformin and long-term PPIs further reduce absorption.

MYTH Vitamin D is just a wellness fad.

FACT Deficiency below 10 ng/mL is a genuine medical problem with real symptoms — bone pain, muscle weakness, frequent infections. In children it causes rickets; in adults, osteomalacia.3

MYTH Fatigue always means you need iron.

FACT Fatigue has many nutritional suspects: B12, vitamin D, folate — and non-nutritional ones like thyroid disease. Testing before supplementing is what finds the actual cause.

What to do next

Suspected deficiency is worked up by risk group and panel, not guesswork:

  1. Check whether you are in a risk group. Vegetarians/vegans (B12, iron, zinc, vitamin D), the elderly (B12, D, calcium, folate), pregnant or breastfeeding women (folate, iron, D, iodine, B12), malabsorption conditions such as coeliac or Crohn’s, long-term PPI or metformin users, indoor workers and people with darker skin (vitamin D).
  2. Ask for the right panel. A nutritional panel typically covers 25-OH vitamin D, serum B12, serum folate, ferritin, and often magnesium, calcium and zinc — ask your doctor what fits your situation.
  3. Understand storage before supplementing. Fat-soluble vitamins accumulate over months (toxicity risk); water-soluble ones do not (deficiency develops faster). This is why indiscriminate high-dose supplementation is riskier than it looks.
  4. Plan pregnancy around folate, not during it. Folate deficiency in the first 28 days of pregnancy — before most women know they are pregnant — raises the risk of neural tube defects. Public health guidance recommends daily folic acid for women planning pregnancy; ask your doctor about the right dose for you.
  5. Recheck after correction. Levels should be remeasured to confirm the deficiency is actually corrected — and the underlying cause (diet, absorption, medication) addressed so it does not recur.

Practical notes

Vitamin levels change over weeks to months, not days, so retesting too soon is rarely useful. After starting correction, doctors typically recheck in two to three months. Keep each report with its date and note the season for vitamin D — levels naturally run lower in winter — along with any symptoms you want to discuss, so trends are read in context rather than as isolated numbers.

Several background facts help interpret vitamin results: all medicines and supplements (metformin and acid-reducing medicines can lower B12; some medicines affect vitamin D), diet pattern (vegan and vegetarian diets are relevant for B12), daily sun exposure and sunscreen habits, any gut conditions or bowel surgery affecting absorption, and alcohol intake.

The lifestyle points doctors commonly raise are sensible sun exposure balanced against skin-cancer risk — your doctor can suggest what that means for your skin type and climate — eating a varied diet with natural vitamin sources, and not self-treating with high-dose supplements: fat-soluble vitamins (A, D, E, K) accumulate in the body and can become toxic in excess.

Follow-up is usually simple: one retest after a couple of months of correction to confirm the level has responded, then less frequent checks. If levels don't budge despite correction, doctors look for absorption problems or check whether the supplement is actually being taken and absorbed — so mention honestly if you keep forgetting doses.

In India

A 25-OH vitamin D test typically costs ₹1,200–₹2,500 and a vitamin B12 test around ₹1,000–₹2,000; combined deficiency panels cost more, though prices vary considerably by city and lab.

Look for NABL-accredited laboratories and imaging centres, which follow standardised quality processes. In major cities, most large labs offer home sample collection for the blood tests. Whatever a lab's website says about normal values, the reference range printed on your own report is the one that counts, since ranges differ between machines and assay methods.

Frequently asked questions

What does a vitamin D level below 20 ng/mL mean?

Below 20 ng/mL is deficient; below 10 ng/mL is severe deficiency. Risk factors include limited sun exposure, indoor lifestyle, darker skin pigmentation, obesity and living at high latitudes — and very few foods naturally contain significant vitamin D, so even people who eat well can be deficient.1

Why is vitamin B12 deficiency often missed?

Its symptoms — fatigue, tingling, memory problems — are attributed to other causes, and the body stores 3–5 years of reserves, so deficiency develops slowly. It is particularly common in vegetarians, vegans and the elderly, since B12 is found almost exclusively in animal products. Severe deficiency causes irreversible nerve damage if untreated.

Which medicines lower vitamin levels?

Metformin (a common diabetes drug) reduces B12 absorption and is usually monitored annually; long-term PPIs such as omeprazole are linked to lower B12 and magnesium. If you take these long-term, ask your doctor whether monitoring is due.

What is the difference between fat-soluble and water-soluble vitamins?

Vitamins A, D, E and K are fat-soluble: absorbed with dietary fat and stored in liver and adipose tissue for months, so deficiency develops slowly but toxicity can accumulate with excessive supplementation. B vitamins and vitamin C are water-soluble: excess is excreted in urine, deficiency develops faster, and toxicity is rare — with the notable exception of vitamin B6, which causes peripheral neuropathy at high doses.

Should I take supplements without testing?

Test first. More is not better with fat-soluble vitamins, since A, D, E and K accumulate and can become toxic — vitamin A excess causes raised intracranial pressure, liver damage and birth defects. A simple blood panel identifies what is actually low before supplementing.2

My vitamin D came back low even in summer — can the result be right?
Yes, it can. Most vitamin D comes from skin exposure to sunlight, and indoor work, sunscreen, darker skin pigmentation and clothing cover mean many people make far less than expected even in sunny months. Very few foods contain meaningful vitamin D, so a low summer result is common and worth discussing with your doctor rather than assuming a lab error.
Do I need to fast before a vitamin D or B12 blood test?
Generally no — vitamin D and B12 can be measured on a non-fasting sample. But if they are part of a wider panel that includes glucose or lipids, the lab may still ask you to fast, so follow whatever the test prescription or lab advises.
Can B12 be low in effect even when the blood level looks borderline normal?
Sometimes. The standard B12 test measures total blood level, but what matters is whether your tissues are getting enough — in borderline cases doctors occasionally check methylmalonic acid (MMA) or homocysteine, which rise when B12 is functionally insufficient. If your level sits near the lower limit, this is worth discussing with your doctor.
Are home finger-prick vitamin test kits reliable?
Quality varies: some kits use accredited partner labs and are reasonable for screening, while others lack validation. A finger-prick result that would change treatment is usually worth confirming with a standard venous sample at an accredited lab — and whatever the kit claims, the reference range on a proper lab report is the one that counts.

References

Sources cited on this page. PubMed links open the original abstract.

  1. Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266–281. PMID 17634462 · doi:10.1056/NEJMra070553
  2. Holick MF. The vitamin D deficiency pandemic: Approaches for diagnosis, treatment and prevention. Rev Endocr Metab Disord. 2017;18(2):153–165. PMID 28516265 · doi:10.1007/s11154-017-9424-1
  3. Munns CF, Shaw N, Kiely M, et al. Global Consensus Recommendations on Prevention and Management of Nutritional Rickets. J Clin Endocrinol Metab. 2016;101(2):394–415. PMID 26745253 · doi:10.1210/jc.2015-2175
Medical Disclaimer: This page is for general educational purposes only and does not constitute medical advice. Always consult a qualified doctor for diagnosis and treatment.
Written and medically reviewed by Suman Konda, Clinical Pharmacist · Sources linked to PubMed · Not medical advice: see our disclaimer