Benefits

• Prevents nutrient deficiencies A
• Prevents chronic disease C

Dose One serving as labeled

Side effects Nausea on an empty stomach; bright-yellow urine (B2, harmless)

Caution

• Check for overlap (vitamin A, zinc, selenium, iron) with any single-ingredient products you take
• Use a prenatal formula during pregnancy

Benefits

• Boosts iron absorption A
• Antioxidant; supports skin collagen production B
• Prevents colds C
• Slightly shortens colds B

Dose RDA about 100 mg · upper limit 2,000 mg

Side effects High doses (2 g+): diarrhea, heartburn; higher kidney-stone risk if you have had stones

Caution

• Keep under 1 g if you have had kidney stones
• Can interfere with some blood tests (glucose strips)

Tip Split doses absorb better. Take with iron

Benefits

• Calcium absorption and bone health A
• Fewer falls and fractures in deficient people B
• Immunity and mood C

Dose Typical 800–2,000 IU · upper limit 4,000 IU

Side effects Excess (10,000 IU+ long term) causes high blood calcium: nausea, thirst, kidney stones

Caution

• Add up the D in your multivitamin and calcium products
• Best practice: test your blood level and adjust the dose

Tip Fat-soluble — take with a meal containing fat

Benefits

• Supports energy metabolism (when deficient) A
• Relieves fatigue (if not deficient) C

Dose As labeled

Side effects Fluorescent-yellow urine (harmless). B6 over 100 mg long term: tingling hands and feet (peripheral neuropathy); B3 flushing

Caution

• Be careful with long-term use of high-dose B6 products

Tip Mildly stimulating — take in the morning

Benefits

• Corrects deficiency in vegans, older adults, after stomach surgery, or on metformin A

Dose RDA 2.4 μg (high doses prescribed for deficiency)

Side effects Rare

Caution

• High-dose folate can mask the symptoms of B12 deficiency

Benefits

• Prevents neural tube defects before and in early pregnancy A
• Lowers homocysteine A

Dose RDA 400 μg · pregnancy 600 μg · upper limit 1,000 μg (from supplements)

Side effects Rare

Caution

• High doses mask B12 deficiency
• Talk to your doctor if you take anticonvulsants or methotrexate

Benefits

• Corrects night blindness and deficiency A
• Skin (if not deficient) C

Dose Upper limit 3,000 μg RAE

Side effects Excess: headache, liver damage, hair loss

Caution

• High doses are contraindicated in pregnancy (birth defects)
• Do not combine with acne medication (isotretinoin)
• Add up the A in multivitamins and cod liver oil

Benefits

• Antioxidant B
• Heart disease prevention C

Dose Upper limit 540 mg α-TE

Side effects High doses increase bleeding tendency

Caution

• Use caution with blood thinners (warfarin, aspirin)
• Stop 2 weeks before surgery

Benefits

• Directs calcium into bone B
• May slow artery calcification C

Dose 90–180 μg

Side effects Rare

Caution

• ⚠ Contraindicated with warfarin (cancels its effect)

Tip Pairs with D3 and calcium

Benefits

• Hair and nails (when deficient) B
• Hair (if not deficient) C

Dose Adequate intake 30 μg (products with 5,000 μg+ are common)

Side effects Rare

Caution

• ⚠ High doses distort lab tests (thyroid, cardiac troponin) — stop 3 days before blood work

Benefits

• Bone health (when diet is low) A
• Fracture prevention (supplement alone) C

Dose Typical 700–800 mg/day including food · upper limit 2,500 mg

Side effects Constipation, bloating; high doses raise kidney-stone risk

Caution

• Doses of 500 mg or less absorb best
• Space 4 hours from thyroid medication (levothyroxine)
• Calcium carbonate needs food; calcium citrate works either way

Benefits

• Constipation (magnesium oxide) A
• Muscle cramps and eye twitching (when deficient) B
• Sleep and migraine prevention B

Dose Typical 300–400 mg · supplement upper limit 350 mg

Side effects Diarrhea (oxide and citrate forms); glycinate is gentler

Caution

• Can build up if you have kidney disease
• Space 2 hours from antibiotics (quinolones, tetracyclines)

Tip Relaxing — take at bedtime

Benefits

• Iron-deficiency anemia A

Dose RDA women 14 mg · men 10 mg (treatment doses by prescription)

Side effects Constipation, heartburn, dark stools

Caution

• Do not take long term unless you are deficient (it accumulates)
• Space at least 1 hour from coffee, tea and milk
• Space 4 hours from thyroid medication

Tip Best absorbed on an empty stomach with vitamin C; take with food if it upsets your stomach

Benefits

• Immunity and wound healing (when deficient) A
• Shortens colds (lozenges at onset) B
• Hair loss and acne C

Dose RDA 8–10 mg · upper limit 35 mg

Side effects Nausea on an empty stomach; long-term high doses cause copper deficiency and anemia

Caution

• Add copper if taking 40 mg+ long term
• Space 2 hours from antibiotics

Benefits

• Antioxidant; thyroid hormone metabolism B
• Cancer prevention C

Dose RDA 60 μg · upper limit 400 μg

Side effects Excess: hair loss, brittle nails, garlic breath

Caution

• Commonly included in multivitamins — watch for doubling up

Benefits

• Blood sugar control C
• Weight loss C

Dose 30–200 μg

Side effects Rare

Caution

• May cause low blood sugar with diabetes medication

Benefits

• Lowers triglycerides (high dose) A
• Prevents cardiovascular events B
• Dry eye and inflammation B
• Mood and cognition C

Dose EPA+DHA 1–2 g combined (2–4 g for triglycerides)

Side effects Fishy burps, loose stools; high doses increase bleeding tendency

Caution

• Use caution with blood thinners and before surgery
• Prevent rancidity: refrigerate, keep out of light

Tip Absorbs best right after a fatty meal

Benefits

• Omega-3 source (phospholipid form) B
• Superior to fish oil C

Dose 500–1,000 mg

Side effects Fishy taste; shellfish allergy

Caution

• Duplicates omega-3 (fish oil)
• Use caution with blood thinners

Benefits

• Slows age-related macular degeneration (AREDS2) B
• Eye strain and vision C

Dose Lutein 10–20 mg

Side effects Yellowish skin with long-term high doses

Caution

• Smokers should avoid products containing beta-carotene

Tip Fat-soluble — take with food

Benefits

• Eases statin muscle pain B
• Supports heart failure treatment B
• Fatigue and anti-aging C

Dose 100–200 mg

Side effects Indigestion; insomnia if taken in the evening

Caution

• May reduce the effect of warfarin

Tip Fat-soluble — take with food

Benefits

• Arthritis pain and inflammation B
• Cancer and dementia prevention C

Dose 500–1,000 mg (enhanced-absorption form)

Side effects Stomach upset; rarely raised liver enzymes

Caution

• Use caution with gallstones or bile duct disease
• Use caution with blood thinners
• Black pepper (piperine) versions can affect how drugs are metabolized

Benefits

• Prevents antibiotic-associated diarrhea A
• Eases IBS symptoms B
• Immunity, eczema, weight C

Dose 1–10 billion CFU

Side effects Gas and bloating in the first 1–2 weeks

Caution

• Talk to a doctor if immunocompromised or you have a central line
• Space 2–3 hours from antibiotics

Tip Empty stomach or with food, as the label says

Benefits

• Constipation and regularity A
• Lowers LDL cholesterol and blood sugar A

Dose Start at 5–10 g/day and increase slowly

Side effects Gas; can worsen blockage without enough water

Caution

• ⚠ Reduces absorption of other drugs and supplements — space 2 hours apart
• Drink plenty of water

Benefits

• Improves liver enzymes (alcohol, fatty liver) B
• Hangovers C

Dose Silymarin 140 mg × 2–3 times a day

Side effects Indigestion, loose stools; ragweed-family allergy

Caution

• Not a substitute for liver disease treatment

Benefits

• Digestion with pancreatic enzyme insufficiency A
• Bloating in healthy people C

Dose Right before meals

Side effects Rare

Benefits

• Knee osteoarthritis pain B
• Cartilage regeneration C

Dose Sulfate 1,500 mg

Side effects Heartburn; shellfish allergy

Caution

• Reports of raised INR with warfarin
• May affect blood sugar in diabetes

Benefits

• Osteoarthritis pain B

Dose 800–1,200 mg

Side effects Stomach upset

Caution

• Use caution with blood thinners

Benefits

• Joint pain and function B

Dose 1.5–3 g

Side effects Stomach upset, headache

Benefits

• Skin hydration and elasticity B
• Joint pain B
• Eaten collagen goes straight to your skin C

Dose 2.5–10 g

Side effects Rare; feeling full

Caution

• Fish or pork allergy (check the source)

Tip Take with vitamin C

Benefits

• Prevents bone loss (osteopenia) B

Dose As labeled

Side effects See calcium

Caution

• K2 is contraindicated with warfarin
• Overlaps with standalone calcium and D products

Benefits

• Jet lag; falls asleep faster B
• Staying asleep C

Dose 0.5–3 mg (prescription-only in some countries)

Side effects Daytime drowsiness, dizziness, vivid dreams

Caution

• Prescription-only in some countries — check local rules before ordering online
• Do not take before driving
• Do not combine with alcohol or sleeping pills

Benefits

• Relaxation and focus B
• Sleep quality C

Dose 100–200 mg

Side effects Rare

Caution

• May lower blood pressure further with BP medication

Tip With caffeine: stay alert with less jitteriness

Benefits

• Stress and anxiety B
• Sleep B
• Testosterone and strength C

Dose 300–600 mg extract

Side effects Drowsiness, stomach upset; rare reports of liver injury

Caution

• Contraindicated in pregnancy
• Raises thyroid hormone — caution with thyroid conditions
• Use caution with sedatives

Benefits

• Fatigue and stress C

Dose 200–400 mg

Side effects Dizziness, dry mouth

Caution

• Use caution with antidepressants

Benefits

• Relaxation and sleep C

Dose 100–300 mg

Side effects Rare

Caution

• May lower blood pressure further with BP medication

Benefits

• Strength and muscle mass (with resistance training) A
• Cognition (older adults, sleep-deprived) B

Dose 3–5 g daily

Side effects Initial 1–2 kg weight gain (water); stomach upset

Caution

• Talk to a doctor if you have kidney disease
• Drink plenty of water

Tip With a meal containing carbs and protein

Benefits

• Muscle building (with training) A

Dose Aim for 1.2–2 g/kg body weight of total protein per day

Side effects Gas with lactose intolerance (whey concentrate)

Caution

• Avoid excess with kidney disease

Benefits

• Alertness and exercise performance A

Dose Upper limit 400 mg/day (3–4 cups of coffee)

Side effects Insomnia, palpitations, anxiety

Caution

• Avoid within 6 hours of bedtime
• Caution with high blood pressure or arrhythmia

Benefits

• Blood flow and exercise performance C
• Erectile function B

Dose 3–6 g

Side effects Diarrhea, cramps; may trigger herpes outbreaks

Caution

• Low blood pressure with BP or ED medication
• Do not take after a heart attack

Benefits

• Fewer cold-sore (herpes) outbreaks B

Dose 1–3 g

Side effects Stomach upset

Benefits

• Fat loss C
• Exercise recovery C

Dose 1–2 g

Side effects Fishy body odor, stomach upset

Caution

• Caution with hypothyroidism or a history of seizures

Benefits

• Fatigue and exercise performance C

Dose 1–3 g

Side effects Rare

Benefits

• Fatigue B
• Immunity and blood sugar C

Dose As labeled (standardized ginsenosides)

Side effects Insomnia, palpitations, headache, raised blood pressure

Caution

• Reports of reduced warfarin effect
• Low blood sugar with diabetes medication
• Caution with high blood pressure or insomnia

Benefits

• Dementia prevention C
• Circulation and tinnitus C

Dose 120–240 mg

Side effects Headache, stomach upset

Caution

• ⚠ Bleeding risk with blood thinners and aspirin
• Stop 2 weeks before surgery
• Caution with a history of seizures

Benefits

• Mild depression B

Dose 300 mg × 3 times a day

Side effects Sun sensitivity, stomach upset

Caution

• ⚠ More drug interactions than any other supplement: antidepressants (serotonin syndrome), weakens birth control pills, immunosuppressants, HIV drugs, blood thinners, heart medication
• Never take on your own if you are on any medication

Benefits

• Lowers LDL cholesterol B

Dose Standardized to monacolin K

Side effects Muscle pain, raised liver enzymes (same compound as a statin)

Caution

• ⚠ Do not combine with a statin
• Caution with grapefruit
• Caution with liver disease

Benefits

• Slightly lowers blood pressure B
• Cholesterol C

Dose 600–1,200 mg

Side effects Bad breath, stomach upset

Caution

• Caution with blood thinners; stop before surgery

Benefits

• Prevents recurrent UTIs B

Dose PAC 36 mg

Side effects Stomach upset

Caution

• Possible warfarin interaction (debated)
• Caution with kidney stones (oxalate)

Benefits

• Enlarged prostate symptoms C

Dose 320 mg

Side effects Stomach upset, headache

Caution

• Caution with blood thinners
• May affect prostate cancer screening (PSA)

Benefits

• Oral and throat antibacterial C

Dose As labeled

Side effects Allergic reactions in people allergic to bees

Caution

• Caution with asthma or bee-sting allergy

Benefits

• PMS and breast tenderness C
• Eczema C

Dose 1–3 g

Side effects Headache, stomach upset

Caution

• Caution with blood thinners
• Caution with a history of seizures

Benefits

• Cholesterol C

Dose 10–20 mg

Side effects Rare

Caution

• Caution with blood thinners

Benefits

• Protein and antioxidants C

Dose 1–3 g

Side effects Stomach upset; beware of heavy-metal-contaminated products

Caution

• Caution with autoimmune disease or phenylketonuria (PKU)

Benefits

• Loosens mucus; chronic bronchitis A
• Antioxidant; liver support B

Dose 600–1,200 mg

Side effects Nausea, sulfur smell

Caution

• Rare bronchospasm in people with asthma

Benefits

• Diabetic neuropathy symptoms B
• Weight and antioxidant C

Dose 300–600 mg

Side effects Nausea, skin rash

Caution

• Low blood sugar with diabetes medication
• Binds minerals — space apart from iron and magnesium
• Space from thyroid medication