WikiCompare live prices on vitamin across Amazon, eBay, Walmart, Target, Best Buy, AliExpress, and curated Awin partner merchants. Most adults benefit from: vitamin D3 2000-5000 IU (almost universally deficient in northern latitudes), magnesium glycinate 200-400mg (calming, sleep aid), omega-3 fish oil 1-2g EPA+DHA. Multivitamins are mostly placebo unless you have specific deficiencies — get a blood test first. For sleep: magnesium + 1-3mg melatonin (not 5-10mg — too much causes morning grogginess). For energy: B12 if vegetarian/vegan. Skip greens powders — they're underdosed compared to actual vegetables. Brands matter: NOW, Thorne, Pure Encapsulations, and Life Extension are third-party tested. Click any card to open the seller's product page; we earn a small affiliate commission at no extra cost to you.
Frequently asked questions about vitamin
What vitamins do most adults actually need?
Three high-value supplements: Vitamin D3 2000-5000 IU (universal deficiency in northern latitudes), magnesium glycinate 200-400mg (sleep + muscle calm), omega-3 fish oil 1-2g EPA+DHA (brain + heart). For vegetarians/vegans: add B12. Skip multivitamins — they're underdosed across the board. Get bloodwork first to identify actual deficiencies before random supplementation.
When is the best time to take vitamins?
With meals (better absorption, less stomach upset). Fat-soluble vitamins (A, D, E, K, omega-3) need dietary fat to absorb — take with breakfast that includes some fat. Magnesium and L-theanine work well at night for sleep. Vitamin C and B-complex are water-soluble — anytime with food. Iron should be taken alone — calcium and dairy block absorption.
Are gummy vitamins as good as pills?
Generally no — gummies have less active ingredient per dose, contain added sugar (2-3g per gummy), and often skip iron and calcium entirely (they make gummies taste bad). Capsules and tablets are more efficient. Liquid vitamins (Garden of Life) absorb fastest. Gummies are fine if they're the only way you'll consistently take vitamins.
Do I need a daily multivitamin?
Not if you eat a varied diet — most people get enough from food. Multivitamins help: pregnant women (prenatal), restrictive diets (vegan, eating disorder recovery), elderly with reduced appetite. Random daily multivitamins for healthy adults provide minimal benefit. Targeted single-nutrient supplementation (based on bloodwork) is more cost-effective.
What's the difference between Vitamin D2 and D3?
D3 (cholecalciferol — animal source) absorbs more efficiently and raises blood levels higher than D2 (ergocalciferol — plant source). Prefer D3 unless vegan, in which case D3 from lichen (Garden of Life, Sports Research) works equivalently. Most prescription Vitamin D is D2; OTC supplements should be D3 for best results.
How do I know if I'm vitamin deficient?
Get bloodwork — ask your doctor for a 'comprehensive metabolic panel + Vitamin D + B12 + iron/ferritin' as a yearly baseline. Symptoms of common deficiencies: fatigue (iron, B12, D), brain fog (B12, D), low mood (D, omega-3), muscle cramps (magnesium, potassium). Don't supplement blindly — too much of certain vitamins (A, iron, calcium) is harmful.
Are expensive vitamins worth more than cheap ones?
Sometimes. Quality matters for: third-party testing certifications (USP, NSF, ConsumerLab), bioavailable forms (methylated B12, magnesium glycinate vs oxide), no fillers or artificial colors. Premium brands (Thorne, Pure Encapsulations, Life Extension, Pure Synergy) verify what's on the label. Costco's Kirkland brand is the best value option with most quality intact.