Every week someone asks me which supplements they should be taking. My honest answer is usually “fewer than you think.” The supplement aisle is built on hope and good marketing, and most of what is on those shelves will do nothing for you except lighten your wallet.

That doesn’t mean supplements are useless. A small handful are backed by real research and are worth considering. This guide is the short list I actually give my clients: what works, who it is for, how much to take, and how to avoid buying something that isn’t what the label says.

First: supplements are the last 5%

Think of your results as a pyramid. The base is eating enough protein and the right amount of food, training consistently, sleeping 7 to 9 hours, and moving during the day. Supplements sit at the very top. If the base isn’t in place, no powder or pill will make up for it. If the base is solid, a few supplements can give you a small extra edge.

Something most people don’t know: in the United States, the FDA does not approve dietary supplements before they are sold. Companies are responsible for their own products, and studies keep finding products that contain less than the label says, more than it says, or ingredients that aren’t listed at all. That is why the “How to buy safely” section below matters as much as the list itself.

Supplements with the strongest evidence

These have the best research behind them. That doesn’t mean everyone needs all of them: each one says who it is for.

1. Creatine monohydrate

The most researched sports supplement there is. It helps your muscles produce energy for short, hard efforts, which over time means a few more reps, more strength and more muscle. It works for women as well as men, and it is one of the few supplements with strong evidence behind it. Most useful if your goal is building strength or muscle.

How much: 3 to 5 grams a day, every day, including rest days. No “loading phase” is needed; it just takes about 3 to 4 weeks to fully build up.
When: whenever you’ll remember. Timing barely matters. Mix it into water, coffee or a shake.
What to buy: plain creatine monohydrate. The fancier forms (HCl, “buffered”, ethyl ester) cost more and aren’t better.
Common worry: you may gain 1 to 2 pounds in the first weeks. That is water stored inside your muscles, not fat and not bloating under the skin.
Safety: well studied and considered safe for healthy adults. If you have kidney disease or any kidney concerns, talk to your doctor first.

2. Protein powder

Protein powder is not magic. It is just food in a convenient form. Its job is to help you reach the daily protein target in your app when meals fall short, which for most of my clients is the hardest nutrition habit to hit.

How much: one scoop is usually 20 to 30 grams of protein. Use it to fill the gap, not to replace meals.
Which kind: whey is the best studied. Choose whey isolate if regular whey upsets your stomach. Plant blends (pea plus rice, for example) work well if you avoid dairy.
Look for: a short ingredient list and at least 20 grams of protein per scoop, with a third-party certification (see below).

3. Vitamin D (if your diet and sun are low)

Many people in Indiana run low on vitamin D, especially from October to April when the sun is too weak for your skin to make much. Low vitamin D is linked to weaker bones and can leave you feeling run down.

Who it is for: people who get little sun, especially in winter, and eat few vitamin D foods (fatty fish, eggs, fortified milk or cereal). Routine blood testing isn’t recommended for healthy adults; your doctor will test if there is a specific reason.
How much: the recommended intake for adults is 600 IU a day (800 IU over age 70), from food and supplements combined. Take vitamin D3 with a meal that contains some fat. If your doctor finds you are low, follow their dose.
Don’t overdo it: the safe upper limit for adults is 4,000 IU a day unless your doctor prescribes more. More is not better.

4. Caffeine (pre-workout, simplified)

Caffeine is the active ingredient that makes most pre-workout products work. It can improve strength, endurance and focus. You don’t need an expensive tub with a “proprietary blend”; a cup of coffee does the same job.

How much: 100 to 200 mg (about 1 to 2 cups of coffee) 30 to 60 minutes before training is plenty for most people.
Daily limit: stay under 400 mg a day from all sources (coffee, tea, soda, energy drinks). If you’re pregnant, the limit is 200 mg a day.
Watch your sleep: caffeine lasts for hours. Avoid it within 8 hours of bedtime, because poor sleep will cost you more than caffeine gives you.
Skip it if it makes you jittery or anxious, raises your heart rate noticeably, or if your doctor has told you to limit it.

Worth it in some situations

Supplement	Who it is for	Notes
Omega-3 (fish oil)	Some people who rarely eat fatty fish (salmon, sardines, trout)	Not automatic: whether it helps depends on your health and your reason for taking it. Two servings of fatty fish a week is the first choice. If you do supplement, about 250 to 500 mg of EPA + DHA a day is common. Ask your doctor if you take blood thinners.
Vitamin B12	Vegans, some vegetarians, adults over 50, and people on metformin or long-term acid reducers	An essential nutrient found almost only in animal foods. If you eat a vegan diet you need it from a supplement or fortified foods. Ask your doctor about the right amount.
Iron	Only if a blood test shows you’re low (common with heavy periods)	Never take iron “just in case”: too much is harmful. Take it as your doctor directs.
Electrolytes	Heavy sweaters, and long (90+ minute) or hot sessions	Sodium is the main one lost in sweat. A salty snack or an electrolyte mix works. Cramps alone aren’t a reason: they often come from fatigue, not low electrolytes.
Fiber (psyllium)	If you fall short of your fiber target: about 25 g a day for women and 38 g for men (ages 19 to 50; a little less after 50)	Food first: fruit, vegetables, beans, oats. Start small and drink plenty of water.
Multivitamin	People with a limited or very low-calorie diet	Insurance, not a performance booster. If you’re pregnant or trying, use a prenatal your doctor recommends.
Magnesium	If your diet is low in nuts, seeds, beans and greens	Evidence that it improves sleep is limited and mixed, so don’t expect much. Stay under 350 mg a day from supplements unless your doctor says otherwise.

Usually not worth your money

Fat burners and “thermogenics”: mostly caffeine plus ingredients with little evidence, and some have caused serious side effects. They don’t replace eating in a calorie deficit.
BCAAs and EAAs: if you’re consistently meeting your protein needs with good protein sources, extra BCAAs or EAAs are generally unnecessary for muscle growth. A protein shake is cheaper and does more.
Testosterone and “hormone balance” boosters: no meaningful effect in healthy people, and some have been found to contain undeclared drugs.
Detox teas and cleanses: your liver and kidneys already do this. Many of these teas are laxatives; the weight you lose is water.
Collagen for muscle: collagen is a low-quality protein for building muscle. Count it toward your protein, but don’t rely on it. Evidence for skin and joints is still mixed.
Anything with a “proprietary blend”: the label hides how much of each ingredient you get, so you can’t tell if the dose is real.

How to buy safely

Because supplements aren’t checked before they are sold, look for a third-party certification seal. These independent groups test products for label accuracy, contaminants and banned substances. Certification greatly reduces the risk, but no seal can guarantee a product is completely safe:

NSF Certified for Sport (widely used by pro and college athletes)
Informed Sport or Informed Choice
USP Verified

Also: buy from the brand’s own site or a major retailer rather than unknown third-party sellers, and be wary of any product that promises fast fat loss, big muscle gains or “clinically proven” results without saying where.

Talk to your doctor first if

you are pregnant, trying to become pregnant, or breastfeeding;
you take any prescription medication (some supplements interact with blood thinners, blood pressure, thyroid and diabetes medications, and antidepressants);
you have a medical condition, especially of the kidneys, liver or heart;
you are under 18;
you have surgery coming up.

Quick reference

Supplement	Typical amount	When	Worth it?
Creatine monohydrate	3 to 5 g a day	Any time, daily	Yes, for most people
Protein powder	20 to 30 g per scoop	When meals fall short	Yes, if you miss your protein target
Vitamin D3	600 IU a day (800 over 70)	With a meal	If your diet and sun are low
Caffeine	100 to 200 mg	30 to 60 min before training	Optional; under 400 mg a day total
Omega-3	250 to 500 mg EPA + DHA	With a meal	Sometimes; depends on your health
Vitamin B12	As your doctor advises	Daily	Yes, if you’re vegan
Iron	As your doctor directs	As directed	Only if a test shows you’re low

Your action plan this week

Before buying anything, check the basics: are you hitting your protein target, sleeping at least 7 hours and training consistently? Fix those first.
If your goal is building strength or muscle, creatine monohydrate (3 to 5 g a day, with a third-party seal) is one of the first supplements worth considering.
If your protein keeps coming up short in the app, add one scoop of protein powder a day.
If you eat a vegan diet, make sure you have a B12 source. If you have heavy periods or feel unusually tired, mention it to your doctor; they can decide whether to check your iron.
Look through what you already take. If it has a “proprietary blend” or promises fat burning, you can probably stop buying it.
Not sure about something? Message me in the app with a photo of the label and I’ll help you read it. For questions about medications, interactions or a health condition, ask your pharmacist or doctor.

Sources

ISSN position stand: creatine (2017)
ISSN position stand: caffeine and exercise performance (2021)
Endocrine Society guideline: vitamin D for the prevention of disease (2024)
NIH Office of Dietary Supplements: vitamin D
NIH Office of Dietary Supplements: vitamin B12
NIH Office of Dietary Supplements: iron
NIH Office of Dietary Supplements: magnesium
NIH Office of Dietary Supplements: omega-3 fatty acids
Dietary Guidelines for Americans (fiber targets)
FDA: how much caffeine is too much?
ACOG: caffeine during pregnancy
FDA: dietary supplements

This guide is general education, not medical advice. Supplements can interact with medications and health conditions. Check with your doctor or pharmacist before starting any supplement.