What Vitamins Should I Take? An Honest Answer

Based on NIH Office of Dietary Supplements guidance · Last reviewed: July 15, 2026 · How we source our content

Stand in any pharmacy's supplement aisle and the implied answer is "all of them." The evidence says something much less profitable: for a generally healthy adult eating a reasonable diet, most supplements do nothing measurable. Large, long-running studies of routine multivitamin use keep finding little to no effect on chronic disease.

But that's only half the story. Specific people have specific gaps — and for them, the right supplement genuinely matters. The whole game is figuring out whether you're one of those people, and for which nutrient. That takes four questions.

Question 1: What does your diet leave out?

This is the most reliable predictor there is. Deficiencies follow exclusions:

• Vegan or vegetarian? B12 is non-negotiable — it exists naturally only in animal foods, and your body's reserve runs out silently over a few years. Iron and omega-3 deserve a watchful eye too. (More in our B12 deficiency quiz.)
• Little or no dairy? Calcium and vitamin D need another route — fortified plant milks, canned sardines, tofu, or a supplement.
• Rarely eat fish? You're likely light on EPA and DHA omega-3s, which are hard to get elsewhere.
• Lots of ultra-processed food, few plants? Magnesium and fiber are the usual casualties — nearly half of Americans under-consume magnesium already.

Question 2: What life stage are you in?

• Could become pregnant? Folic acid (400 mcg daily) is the single best-evidenced supplement there is — it prevents neural tube defects in the earliest weeks, before most people know they're pregnant.
• Pregnant? Iron needs jump to 27 mg/day and a prenatal vitamin is standard care — this one belongs with your doctor or midwife.
• Over 65? Two things change quietly: skin makes less vitamin D, and the stomach frees less B12 from food. Both are worth checking at this age even without symptoms.
• Menstruating, especially heavily? Iron loss is real and cumulative — but confirm with a ferritin test before supplementing (our iron page explains why that order matters).

Question 3: What does your lifestyle limit?

• Indoors most days, northern winters, consistent sunscreen, darker skin? Each independently raises vitamin D risk; combined, deficiency becomes more likely than not in winter.
• Heavy training? Endurance athletes — runners especially — burn through iron faster than average.
• Regular medications? Metformin and long-term acid reducers deplete B12; daily PPIs and diuretics drain magnesium. Few people are told this when prescribed.
• Alcohol most days? Magnesium, B1 and folate all suffer.

Question 4: What are your symptoms telling you?

Symptoms are the noisiest signal of the four — everything overlaps with stress and poor sleep — but they're far from useless, especially in combination. Unexplained exhaustion has three usual nutritional suspects (iron, B12, vitamin D), and the accompanying details usually separate them: pale skin and breathlessness lean iron; tingling and brain fog lean B12; low winter mood and muscle aches lean vitamin D. Cramps and twitches point at magnesium.

This cross-referencing is what our free assessment actually does: it walks all four questions systematically — diet, life stage, lifestyle, symptoms — and ranks which deficiencies fit your pattern, screening 12+ nutrients at once. It doesn't sell supplements, so it has no reason to tell you that you need one.

And what you probably don't need

A few honest subtractions, since nobody selling supplements will make them:

• A "just in case" multivitamin — fine as cheap insurance, but don't expect to feel different, and it won't fix a real deficiency; the doses are too low.
• Megadoses of anything — fat-soluble vitamins (A, D, E, K) accumulate; high-dose vitamin A harms liver and bone, and even B6 causes nerve damage in gram-range doses.
• Iron without a blood test — the body can't easily excrete excess, and 1 in 300 people carries hemochromatosis. Test, then treat.
• The 12-item influencer stack — if you can't say which gap each item fills, it's decoration.

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