Vitamins & supplements
Fill the gaps.
Protect your muscle.
Check with your doctor: Verify everything here with your doctor and with your own research. Show this to your doctor to see if they agree these vitamins, supplements and workouts are safe for you, especially if you take medicines, are pregnant or have a health condition.
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Vitamins & supplements
- 8
- Goal-based stacks
- PubMed
- Verified studies
- Every item
- Has a warning
By goal
Tap a goal to open it. Each one shows amounts, warnings and the studies behind them.
Mitochondria & energyYour cells have tiny batteries called mitochondria. These help clean out old batteries, protect the rest and give them the raw materials to work.
Urolithin A
Turns on the clean-up crew (mitophagy) that clears out worn-out mitochondria.
How much: 500–1,000 mg once a day with a meal, for about 12 weeks, then reassess with your doctor.
Warning: Well tolerated in trials of up to 4 months. Choose a product that states the urolithin A amount (not just “pomegranate extract”).
Proof: Randomized trials in older and middle-aged adults found better muscle endurance, strength and mitochondrial markers over 4 months. Study (PMID 35050355)Study (PMID 35584623)
GlyNAC (glycine + NAC)
Gives your body the two building blocks it needs to make glutathione, its main antioxidant.
How much: Typical products: glycine 1.8–3 g plus NAC 600–1,200 mg a day. The trials used larger, body-weight-based doses under supervision.
Warning: NAC can add to the blood-sugar-lowering effect of berberine or metformin, and interacts with nitroglycerin. Avoid very high NAC doses (over 3 g a day) without medical oversight.
Proof: In a small randomized trial of older adults, 16 weeks of GlyNAC improved glutathione, oxidative stress, mitochondrial function, inflammation and strength measures compared with placebo. Study (PMID 35975308)
Benfotiamine (vitamin B1)
A well-absorbed form of vitamin B1, which your mitochondria need to make energy from food.
How much: 300–600 mg a day.
Warning: Generally well tolerated; rare allergic reactions. On a GLP-1 with lots of vomiting or very low intake, ask your doctor to check thiamine (B1).
Proof: Studied mainly for nerve and brain health; a phase IIa trial used 300 mg twice daily. Benefits for energy in healthy people are not proven. Study (PMID 33074237)
Magnesium L-threonate
A form of magnesium that reaches the brain; supports deep sleep, when much repair happens.
How much: 1,500–2,000 mg of the compound (about 110–145 mg elemental magnesium), 1–2 hours before bed.
Warning: Counts toward the 350 mg a day elemental magnesium limit from all supplements. Ask first with kidney disease.
Insulin resistance & blood sugarInsulin is a key that lets sugar into your cells. With insulin resistance the locks get rusty; these help clean the locks, alongside exercise, sleep and fat loss.
Berberine
A plant compound that switches on AMPK, the cell's “low fuel” sensor, similar to some effects of metformin.
How much: 500 mg two or three times a day with meals (1,000–1,500 mg a day).
Warning: Can lower blood sugar, so take care with diabetes medicines. It slows the breakdown of many drugs (some statins, blood thinners, heart-rhythm drugs, antidepressants, cyclosporine): check with your pharmacist. Not for pregnancy or breastfeeding.
Proof: Meta-analyses of trials in type 2 diabetes found lower fasting glucose and HbA1c; triglycerides also improve. Study (PMID 36467075)Study (PMID 30393248)
Myo-inositol + D-chiro-inositol
Helps the insulin signal work inside cells.
How much: Myo-inositol 2 g twice a day plus D-chiro-inositol 50 mg twice a day (a 40:1 ratio).
Warning: Mild stomach upset at higher doses. Talk to your doctor if you take diabetes medicines.
Lactoferrin
A milk protein that binds iron; studied for reducing belly fat.
How much: About 300 mg a day of enteric-coated lactoferrin for 8 weeks, as in the trial.
Warning: Avoid with a milk-protein allergy. Effects beyond the trial period are not known.
Proof: A small placebo-controlled trial in Japanese adults with abdominal obesity found less visceral (deep belly) fat after 8 weeks. Study (PMID 20691130)
Resistant starch (food)
Starch your gut bacteria ferment, which helps release your own fullness hormones (GLP-1 and PYY).
How much: Cook rice, pasta or potatoes, then refrigerate 12–24 hours before eating; or 1–2 tablespoons of green banana flour or raw potato starch in cold food.
Warning: Start with 1 tablespoon and build up slowly to avoid gas and bloating.
Benfotiamine (vitamin B1)
Supports nerves exposed to high blood sugar and covers B1 when you eat less.
How much: 300–600 mg a day.
Warning: Not a replacement for blood-sugar treatment. Rare allergic reactions.
PCOS (women)PCOS is closely tied to insulin resistance. These support insulin, cycles and hormone balance alongside your doctor's care.
Myo-inositol + D-chiro-inositol
Improves insulin signaling, cycle regularity and ovulation markers in some women.
How much: 4 g myo-inositol plus 100 mg D-chiro-inositol a day (40:1).
Warning: Evidence quality is limited and results vary. Tell your doctor if you're trying to conceive or take fertility or diabetes medicines.
Proof: A 2024 meta-analysis informing the international PCOS guideline found possible metabolic benefits but limited evidence overall. Study (PMID 38163998)
Omega-3 (EPA + DHA)
May lower inflammation and triglycerides.
How much: 1–2 g a day of EPA + DHA.
Warning: Check with your doctor if you take blood thinners.
Vitamin D
Deficiency is common in PCOS; correcting it may help insulin sensitivity.
How much: Dose based on your 25-OH vitamin D blood test.
Warning: Don't take high doses without testing.
Thyroid supportYour thyroid needs certain minerals to make and activate its hormones.
Selenium
Helps convert thyroid hormone T4 into the active T3 and protects the thyroid.
How much: 100–200 mcg a day. Never more than 400 mcg a day.
Warning: Too much selenium is toxic (hair and nail loss, nerve problems). Count selenium from multivitamins and Brazil nuts.
Proof: In Hashimoto's thyroiditis, a 2024 meta-analysis of randomized trials found selenium lowered thyroid antibodies. Study (PMID 38243784)
Zinc
Supports thyroid hormone production and immunity.
How much: 15–30 mg a day with food.
Warning: Over 40 mg a day long-term can lower copper; get copper checked if you take it for months.
Vitamin D3
Supports immune balance; low levels are linked to autoimmune thyroid problems.
How much: Usually 1,000–4,000 IU a day, based on your blood level.
Warning: Above 4,000 IU only with your doctor and blood tests.
Omega-3 fish oil
Helps lower inflammation.
How much: 1–2 g a day of EPA + DHA.
Warning: Check with your doctor if you take blood thinners.
Testosterone & hormone supportThese support your body's own hormone production. They don't replace medical treatment: get your hormone panel first.
Zinc
Needed to make testosterone; low zinc is linked to low testosterone.
How much: 25–40 mg a day with food.
Warning: Stay at or under 40 mg a day long-term (the upper limit). Pair with copper if you take it for months.
Vitamin D3 + K2
Higher vitamin D is linked to healthier testosterone; K2 helps direct calcium to bones.
How much: D3 based on your blood level (often 1,000–4,000 IU) plus 100–200 mcg K2 (MK-7).
Warning: Higher D3 doses only with your doctor and blood tests. K2 interacts with warfarin.
Magnesium glycinate
Improves sleep, which drives testosterone, and may free up more active testosterone.
How much: 200–350 mg elemental before bed.
Warning: Total supplemental magnesium at or under 350 mg elemental a day unless your doctor advises more.
Ashwagandha (KSM-66)
May lower cortisol; small studies report improved testosterone and sleep.
How much: 300–600 mg a day.
Warning: Rare reports of liver injury. Avoid in pregnancy, with thyroid medication or autoimmune disease unless your doctor agrees. Stop if you notice dark urine or yellow skin.
Boron
Small studies suggest it may raise free testosterone.
How much: 6–10 mg a day.
Warning: Evidence is small and short-term. Stay well under 20 mg a day.
Tongkat ali
May support testosterone and lower stress hormones in small studies.
How much: 200–400 mg standardized extract a day.
Warning: Product quality varies and some have been contaminated; choose third-party-tested brands.
InflammationLower background inflammation helps recovery, joints and heart health.
Extra virgin olive oil
Rich in polyphenols with mild anti-inflammatory effects; a core of the Mediterranean diet.
How much: 1–2 tablespoons a day.
Warning: It's still calorie-dense; use it in place of other fats.
Curcumin with piperine
Turns down inflammatory pathways (NF-κB).
How much: 500–1,000 mg a day of standardized curcuminoids.
Warning: May interact with blood thinners and diabetes medicines. Avoid with gallstones or bile-duct problems. Rare liver injury reported with high-absorption products.
Proof: Meta-analyses of randomized trials found lower inflammation markers (CRP, IL-6) and less arthritis pain. Study (PMID 36804260)Study (PMID 35935936)
Omega-3 fish oil
Helps lower inflammation and triglycerides.
How much: 1–2 g a day of EPA + DHA.
Warning: Check with your doctor if you take blood thinners or have a procedure coming up.
Black seed oil
May help inflammation, blood sugar and cholesterol in small studies.
How much: 500 mg twice a day, or about 1–2.5 mL of the oil.
Warning: Can lower blood pressure and blood sugar: use medical supervision if you take blood-pressure or diabetes medicines or insulin.
GLP-1 gut, reflux & bile supportGLP-1 medicines slow your stomach, which can bring reflux, nausea and constipation. These soothe and protect.
Alginate raft (e.g. reflux raft products)
Forms a floating gel on stomach acid that blocks reflux.
How much: After meals and before bed, as labeled.
Warning: High-sodium formulas: careful with high blood pressure, heart failure or kidney disease. Take 2 hours apart from medicines.
DGL (deglycyrrhizinated licorice)
Helps the stomach and esophagus make protective mucus.
How much: 380–760 mg chewable, 20 minutes before meals.
Warning: Use DGL, not regular licorice, which raises blood pressure. Caution with blood-pressure medicines, diuretics, kidney disease and pregnancy.
Slippery elm
Coats the throat and esophagus with a protective layer.
How much: 400–500 mg capsules, 3–4 times a day before meals or bed.
Warning: Take 2 hours apart from all medicines and supplements.
Zinc carnosine
Supports healing of the stomach and gut lining.
How much: 37.5 mg twice a day with meals.
Warning: Contains zinc: count it toward your daily total and don't exceed 40 mg a day long-term.
TUDCA
A bile acid that supports bile flow and the liver, useful during rapid weight loss.
How much: 500–1,500 mg a day, split into doses.
Warning: Can cause diarrhea or stomach upset. Rapid weight loss raises gallstone risk: report right-upper belly pain, fever or yellow skin to your doctor.
Fiber and electrolytes
For constipation and fluid loss from GI side effects.
How much: Psyllium 5–10 g a day with water; electrolytes on rough days.
Warning: Increase fiber slowly; separate from medicines by 2 hours. Extra sodium needs care with high blood pressure.
Protein & muscleProtein is the raw material for muscle. On a GLP-1 or a diet, it's the first thing to protect.
Food protein first
Chicken, fish, eggs, Greek yogurt, lean beef, cottage cheese, tofu.
How much: About 1.2–1.6 g per kg of body weight a day, spread over meals.
Warning: Kidney disease: get a protein target from your doctor.
Whey protein
Easy protein when appetite is low.
How much: 20–40 g per serving.
Warning: Choose third-party-tested products; use a lactose-free isolate if dairy bothers you.
Essential amino acids (EAA)
All nine amino acids muscle needs, in a small dose, when eating is hard.
How much: 10–15 g a day, especially around training.
Warning: Better than BCAA, which only contains three of the nine.
Creatine monohydrate
The best-studied supplement for strength and muscle.
How much: 3–5 g a day.
Warning: Ask first with kidney disease. It can raise the creatinine number on blood tests without kidney harm; tell your doctor you take it.
Sleep & calm
Can't sleep or feeling wired? These have the most research behind them.
Calm & resilience stackL-theanine by day; glycine, magnesium and chamomile in the evening.
L-theanine
An amino acid from tea that calms a racing mind without making you drowsy. When: Morning or afternoon for calm focus, or in the evening to unwind.
How much: 200–400 mg a day (studies mostly used 200 mg).
Warning: Can add to the effect of blood-pressure and sedating medicines. Not well studied in pregnancy.
Proof: A 4-week randomized trial in healthy adults (200 mg/day) improved stress-related symptoms and sleep; a 2026 review of 31 randomized trials found modest benefits for stress. Study (PMID 31623400)Study (PMID 42410082)
Glycine
An amino acid that helps lower your body temperature at night, a natural signal for deep sleep. When: 30–60 minutes before bed; it mixes easily into chamomile tea.
How much: 3 g (about 1 teaspoon of powder).
Warning: Generally well tolerated; can cause a mild upset stomach. Avoid if you take clozapine, and check with your doctor if pregnant.
Proof: In sleep-restricted volunteers, 3 g before bed reduced next-day sleepiness and fatigue; a 2026 review summarizes the sleep studies, which are small. Study (PMID 22529837)Study (PMID 42687500)
Magnesium glycinate
A gentle, well-absorbed form of magnesium that helps muscles relax and supports sleep. When: Evening, 30–60 minutes before bed.
How much: 100–350 mg of elemental magnesium (check the label; it's different from the total mg of the capsule).
Warning: Keep all supplemental magnesium at or under 350 mg elemental a day unless your doctor advises more. Avoid with kidney disease unless approved. Can loosen stools.
Proof: In older adults with insomnia, magnesium improved sleep measures in a randomized trial; a 2021 meta-analysis called the evidence promising but low quality. Study (PMID 23853635)Study (PMID 33865376)
Magnesium L-threonate
A form of magnesium marketed for the brain, sleep quality and mental recovery. When: Evening, 1–2 hours before bed.
How much: Products are usually 1,500–2,000 mg of the compound, which is only about 110–145 mg of elemental magnesium.
Warning: Counts toward the same 350 mg elemental magnesium limit as glycinate: add both labels together if you take both.
Proof: A 2025 randomized, placebo-controlled trial reported better sleep quality and some cognitive measures; independent research is still limited. Study (PMID 41601871)
Chamomile tea
A calming herbal tea that can help you wind down. When: In the hour before bed.
How much: 1 cup, steeped 5–10 minutes.
Warning: Avoid if you're allergic to ragweed, daisies or related plants. May interact with blood thinners such as warfarin.
Proof: Meta-analyses of clinical trials (2019, 2024) found improvements in sleep quality and anxiety, though studies are small. Study (PMID 39106912)Study (PMID 31006899)
The basics
Protein
In simple words: The building block for muscle. On a GLP-1 you eat less, so protein is the first thing to protect.
- How much
- A common target during weight loss is 1.2–1.6 g per kg of body weight a day, spread over meals (ask your clinician or dietitian).
- Who might need it
- Everyone losing weight, people on GLP-1 medicines, adults over 50.
- Food first
- Eggs, Greek yogurt, fish, chicken, lean meat, tofu, beans; a protein shake if appetite is very low.
Be careful: If you have kidney disease, get a protein target from your clinician.
Multivitamin
In simple words: A basic safety net when you are eating smaller meals.
- How much
- One a day of a standard multivitamin/mineral, as on the label.
- Who might need it
- People eating much less than usual, including on GLP-1 medicines.
- Food first
- A varied diet with vegetables, fruit, whole grains and protein still comes first.
Be careful: Avoid stacking several multis or high-dose products on top of one.
Vitamin D3
In simple words: Helps your bones, muscles and immune system. Many people are low, especially in winter.
- How much
- Recommended intake is 600 IU a day (800 IU over 70); many people take 1,000–2,000 IU. Upper limit for adults: 4,000 IU a day unless your clinician advises more.
- Who might need it
- Little sun exposure, darker skin, over 65, low blood level on testing.
- Food first
- Oily fish, eggs, fortified milk and cereals.
Be careful: Test your 25-OH vitamin D level before taking high doses. Often paired with vitamin K2, though evidence for the pairing is limited.
Vitamin B12
In simple words: Keeps your nerves and blood healthy and helps with energy.
- How much
- Recommended intake is 2.4 mcg a day; supplements commonly contain 250–1,000 mcg.
- Who might need it
- People taking metformin or acid-reducing medicines, vegans, adults over 50, anyone eating very little.
- Food first
- Fish, meat, eggs, dairy, fortified foods.
Be careful: Ask for a B12 blood test if you have tingling, numbness or unusual tiredness.
Magnesium
In simple words: Helps muscles relax, sleep and regularity. Different forms do different jobs.
- How much
- From supplements, stay at or under 350 mg of elemental magnesium a day unless your clinician advises otherwise. Glycinate is gentle (often taken in the evening); citrate helps constipation.
- Who might need it
- Poor sleep, muscle cramps, constipation (common on GLP-1 medicines).
- Food first
- Nuts, seeds, leafy greens, beans, whole grains, dark chocolate.
Be careful: Magnesium L-threonate is marketed for sleep and memory (products are often 1,500–2,000 mg, about 110–145 mg elemental magnesium), but human evidence is still limited. Avoid supplements with kidney disease unless your clinician approves.
Omega-3 (fish oil)
In simple words: Healthy fats for your heart, and possibly a small help for muscle in older adults.
- How much
- Commonly 250–1,000 mg of EPA + DHA a day; higher amounts only with your clinician.
- Who might need it
- People who rarely eat oily fish.
- Food first
- Salmon, sardines, mackerel, trout; walnuts and flax give a plant form.
Be careful: Talk to your clinician if you take blood thinners or have a procedure coming up.
Fiber (psyllium)
In simple words: Keeps you regular and helps blood sugar. Very useful for GLP-1 constipation.
- How much
- Aim for 25 g (women) to 38 g (men) of fiber a day from food; psyllium 5–10 g a day can top it up.
- Who might need it
- Constipation, eating less food overall.
- Food first
- Vegetables, fruit, beans, lentils, oats, chia and flax.
Be careful: Increase slowly and drink plenty of water. Take it 2 hours apart from other medicines.
Electrolytes
In simple words: Sodium, potassium and magnesium you lose through sweat, vomiting or diarrhea.
- How much
- As labeled, on days you sweat a lot or have GI side effects.
- Who might need it
- People with GLP-1 nausea, vomiting or diarrhea; long Zone 2 or hot-weather sessions.
- Food first
- Broth, fruit, vegetables, a pinch of salt in water.
Be careful: Check with your clinician first if you have high blood pressure, heart failure or kidney disease.
Calcium
In simple words: Strong bones, especially after menopause and as you age.
- How much
- 1,000–1,200 mg a day in total from food plus supplements; take no more than about 500 mg at once.
- Who might need it
- Low dairy intake, women after menopause, adults over 70.
- Food first
- Dairy, fortified plant milks, canned salmon or sardines with bones, leafy greens.
Be careful: Food is the preferred source; very high supplement doses may raise kidney stone risk.
Iron
In simple words: Carries oxygen in your blood. Only take it if a blood test shows you're low.
- How much
- Only as directed after a ferritin or iron test.
- Who might need it
- Menstruating women, heavy periods, vegetarians, people with a low blood test.
- Food first
- Red meat, poultry, fish, beans, lentils, fortified cereals (with vitamin C to absorb more).
Be careful: Too much iron is harmful. Don't take it 'just in case'.
Creatine monohydrate
In simple words: The best-studied supplement for strength and muscle. Helps protect muscle while losing weight.
- How much
- 3–5 g a day, any time of day; no loading phase needed.
- Who might need it
- Anyone strength training, adults over 50, people on GLP-1 medicines who lift.
- Food first
- Small amounts in meat and fish.
Be careful: Ask first if you have kidney disease. It can raise the creatinine number on blood tests without kidney harm; tell your clinician you take it.
Supplements aren't reviewed by the FDA for safety or effectiveness before they're sold. Choose third-party-tested products (look for USP, NSF or Informed Sport seals), and check with your clinician or pharmacist about interactions with your medicines.
Not sure what you're low in? Check the bloodwork guide for the tests to ask your doctor for.
Amounts follow NIH Office of Dietary Supplements fact sheets. General education, not medical advice.