Persistent tiredness is the symptom people apologise for. It is also how both of these deficiencies usually announce themselves — quietly enough to be blamed on work, heat, age or sleep for years before anyone tests for them.
Vitamin D
Vitamin D is made in the skin under direct sunlight and is essential for absorbing calcium — which makes it a bone hormone as much as a vitamin. Deficiency is common across India despite the sunshine, and the reasons are unremarkable ones:
- Indoor work through the hours when sunlight is strong enough to matter
- Deliberate sun avoidance, full-cover clothing and daily sunscreen
- Deeper skin pigmentation, which needs longer exposure for the same synthesis
- Very little in a typical vegetarian diet, which contributes almost none
- Older age, obesity, and conditions that reduce absorption from the gut
What it feels like
Aching bones — especially the lower back, hips and thighs — muscle weakness that shows up on stairs, fatigue, frequent infections, low mood, and in children, delayed milestones or bowed legs. Many people have no symptoms at all until a fracture or a routine test.
The test
Ask for 25-hydroxy vitamin D, written 25(OH)D. This is the storage form and the correct measure of status. The 1,25-dihydroxy form is a specialist test for particular conditions and is not the one to order for a general check — it can even be normal in someone deficient.
Fasting is not required. Read the result against the range printed on your own report; laboratories and methods differ, and most flag deficiency below 20 ng/mL and insufficiency between 20 and 30 ng/mL.
Vitamin B12
B12 comes almost entirely from animal foods — meat, fish, eggs and dairy. A long-standing vegetarian or vegan diet is the single biggest reason for deficiency in India, and dairy alone often does not carry enough.
Absorption is the other half of the story. B12 needs stomach acid and a protein called intrinsic factor to be taken up in the last part of the small intestine. Several ordinary things get in the way:
- Metformin, taken long term for diabetes, lowers B12 in a meaningful proportion of users
- Acidity medicines (proton pump inhibitors such as pantoprazole and omeprazole) taken for months or years
- Age above 60, as stomach acid production falls
- Pernicious anaemia, coeliac disease, and previous gastric or intestinal surgery
What it feels like
B12 deficiency affects both blood and nerves. Fatigue and breathlessness come from anaemia; tingling or pins-and-needles in the hands and feet, numbness, unsteadiness, a sore red tongue, mouth ulcers, poor concentration and memory lapses come from the nervous system.
The nerve symptoms matter because prolonged, untreated deficiency can cause damage that does not fully reverse. Tingling in the feet in someone on long-term metformin is worth a test, not a wait.
The test
A serum vitamin B12 level is the starting point. It has a known weakness: it measures total B12, including a fraction the body cannot use, so a borderline-normal level can sit on top of a real deficiency at the tissue level.
When the level is borderline but the symptoms fit, doctors add homocysteine or methylmalonic acid (MMA), both of which rise when B12 is genuinely lacking inside cells. A complete blood count is often ordered alongside, as B12 deficiency classically enlarges red blood cells.
One practical point: if you have already started B12 tablets or injections, the level is no longer interpretable. Test before starting, or tell your doctor exactly when you started.
Who should get tested
- Anyone with unexplained fatigue, bone or muscle pain, or tingling in the hands and feet
- Long-term vegetarians and vegans (B12), and people who see little direct sunlight (vitamin D)
- Adults on long-term metformin or acidity medication (B12)
- Pregnancy and planned pregnancy, and older adults
- Anyone who has had a fragility fracture, or who is being treated for osteoporosis (vitamin D)
Both tests are part of our full-body health packages, and can be booked individually — vitamin D is listed with bone and joint health tests. Sample collection at home is available across Surat if a visit is inconvenient.
After the result
Correction is your doctor's prescription, not a supplement aisle decision, and the doses used for deficiency are much higher than the ones in a daily multivitamin. Two things worth knowing:
- Do not self-dose high-strength vitamin D for months on end. It is fat-soluble, it accumulates, and excess raises blood calcium — which is genuinely harmful. Weekly sachets are prescribed for a defined period for exactly this reason.
- Retest at the right time. Vitamin D is usually rechecked around 8 to 12 weeks after starting treatment, once stores have had time to fill. B12 is reviewed on symptoms and blood counts rather than by chasing the number.
Neither of these is an exotic diagnosis. They are two of the most common correctable causes of feeling unwell for a long time — which is the whole argument for testing rather than assuming.
- Vitamin D
- Vitamin B12
- Preventive testing
