A GP's checklist for 14 common supplements: how to take each one so it works, what not to combine, and how to read the label.
Most of the supplements my patients bring in aren't the wrong ones. They're taken the wrong way, doubled up across products, or bought in a form that doesn't deliver the dose on the label.
I always ask what supplements a patient takes, because the answer can change my clinical decisions. That means keeping up with what's on the shelf and the science behind it, which moves quickly. Some products are genuinely helpful. Some interact with medicines the person already takes. Some have no real data behind their claims, or come from companies without a strong record for quality.
From there, we cover the basics: which supplements correct a genuine deficiency, and how the different forms and brands compare. And almost always, before they leave, patients ask what I take myself. So here is how to get the most from the common ones, with my own short list at the end.
Why so many of us take supplements
In a nationally representative survey of 2,019 Australian adults published in BMJ Open, half were using a complementary medicine product, and 47.8% were taking a vitamin or mineral supplement.
My advice always starts with whole foods, from both sides of the plate. No capsule copies a varied plate.
The trouble is that most Australians fall short. In the ABS National Health Survey 2022, only 6.5% of adults ate the recommended serves of vegetables. The ABS National Nutrition and Physical Activity Survey 2023 found that six in ten Australians did not get enough calcium from their diet, and almost half of women aged 18 to 29 fell short on iron.
The reasons are practical. In the Heart Foundation's State of the Heart 2025 survey of more than 5,000 adults, the barriers named most often were the cost of healthy food and the convenience of less healthy options. The ACCC's supermarkets inquiry found Woolworths and Coles hold about two thirds of supermarket grocery sales between them, which it described as an oligopoly with limited incentive to compete hard on price. In my part of Sydney, a good independent greengrocer is harder to find than it used to be.
So people reach for supplements, and I understand why. Used well, they bridge a gap while you work on the food.
How to take the common ones so they work
A good product taken the wrong way wastes your money. This is the checklist I run through when a patient empties their bag of bottles on my desk.
Supplement | How to take it | Watch for |
|---|---|---|
Vitamin D | With a meal that contains some fat. Time of day matters less than taking it with food. D3 is more stable and better absorbed than D2. Vegan D3 is made from algae or lichen. | Long term high doses without a blood test. Interacts with some diuretics and steroids. Check whether your multivitamin already contains it. |
Creatine | 3 to 5 grams a day, any time. Loading is optional: 3 grams a day for 28 days fills muscle stores as well as a week of loading. Higher doses have been studied for thinking under stress, such as sleep deprivation, but that evidence is emerging and the right dose isn't known. More in my creatine article. | A gain of 1 to 2 kg early on, mostly water. Powder is more reliable than gummies. Check with your doctor first if you have kidney disease. |
Protein powder | Use it to close the gap to your daily target, not to replace meals. Plant blends such as pea with faba bean or rice can cover all nine essential amino acids. | Check the leucine per serve, and the full amino acid profile for plant blends. |
Greens and multi nutrient powders | A convenient top up when fruit and vegetable intake is low. Read the dose of each vitamin and mineral per scoop. | Count what they contain toward your daily totals from other products, especially B6, vitamin D and iron. |
Vitamin B12 | Important for vegans, vegetarians who eat few eggs or dairy, and many older adults. The body stores B12, so a high dose tablet a couple of times a week is enough for many people. | Ask for a blood test if you are tired, numb or tingling. |
Folic acid | 400 micrograms daily from one month before pregnancy through the first three months. Some women need a higher dose, so check with your doctor. People who eat plenty of plant foods usually get enough folate from food. | A high folate intake can hide the blood signs of low B12, so vegans should have B12 checked too. |
Iron | Only if a blood test shows you are low. Most likely in menstruating women (especially with heavy periods), pregnancy, vegetarians and vegans, and regular blood donors. Take it with vitamin C, and away from tea, coffee and calcium. Gentler forms such as iron bisglycinate may upset the stomach less. | Constipation and stomach upset. Too much iron causes harm. |
Zinc | With food if it upsets your stomach. Vegans may need more, because compounds in grains and legumes reduce absorption. | Long term high doses can lower copper. Avoid taking it at the same time as high dose iron. |
Iodine | 150 micrograms a day for adults who need it, mainly vegans and anyone planning a pregnancy, pregnant or breastfeeding. | Too much is also harmful. Kelp based products can vary in content. Check first if you have a thyroid condition. |
Calcium | Food first. If you need a supplement, 500 mg or less at a time absorbs best, and carbonate forms work better with a meal. | Keep it apart from iron and thyroid medicine. Count calcium from fortified foods and other products. |
Selenium | Most people get enough from food, and a little goes a long way. | The gap between enough and too much is narrow. Avoid doubling up across products. |
Omega-3 | With a meal. Vegans can use algae based EPA and DHA. | Tell your doctor if you take a blood thinner. |
Magnesium | Check the amount of magnesium itself, not the weight of the compound. The form matters. Glycinate is gentler on the gut and is often chosen for sleep and muscle cramps, though the evidence for those uses is modest. | Oxide and citrate forms can loosen the bowels. Check with your doctor first if you have kidney disease. |
Pre, pro and postbiotics | Prebiotics feed your gut bacteria. Probiotic benefits are specific to the strain and dose studied, so look for full strain names on the label. More on the difference below. | Start low to limit bloating. Talk to your doctor first if your immune system is weakened. |
Prebiotics, probiotics and postbiotics: what's the difference?
These three words now appear on almost every gut product, and most people use them interchangeably. They mean different things.
Prebiotics are food for the bacteria already in your gut, usually fibres such as inulin, beta glucan or resistant starch. Your gut bacteria ferment them into compounds that help keep the gut lining healthy. Vegetables, legumes, oats and slightly green bananas are natural sources.
Probiotics are live microorganisms that give a health benefit when taken in adequate amounts. The benefit belongs to the specific strain and dose studied, which is why a full strain name on the label matters more than a large number of strains.
Postbiotics are inactivated microorganisms, or parts of them, that still give a health benefit. Because they aren't alive, they don't need to survive the trip to your gut.
Fibre itself does a lot of the work. If you eat plenty of plants, you're already feeding your gut well. A supplement is most useful when your diet falls short.
All in one powders: are they worth it?
All in one greens and nutrient powders are one of the fastest growing parts of the market, and some of the biggest brands are backed by athletes and celebrities. An endorsement tells you about the marketing budget, not the formula.
Used well, a good all in one powder is a convenient way to cover small gaps on busy days, and a better choice than a pantry of single products you forget to take. What a doctor or dietitian would add is a step before it. Find out what you actually need first, with a look at your diet and, where it helps, a blood test. A measured gap, such as low vitamin D, B12 or iron, often needs a targeted dose that an all in one won't provide.
Before you buy one, ask the same questions as any supplement. Does it list the dose of every ingredient, or hide them in a blend? Has the finished product been independently tested? Does it overlap with what you already take? A brand that answers all three clearly is worth a look.
Is plant protein as good as whey?
It can be, if you choose well. Protein is built from amino acids. Your body makes some of them, but nine it cannot make, so they have to come from food. These are the essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
Animal proteins contain all nine in useful amounts. Many plant proteins run low in one. Grains tend to be low in lysine, and legumes such as peas tend to be low in methionine. That's why many plant powders blend pea with rice, so each fills the other's gap. Soy contains all nine on its own.
Leucine deserves a mention because it acts as a signal for muscle building, not just a building block. Look for about 2 grams of leucine per serve on the label. Many good plant blends reach it.
How much protein? For people who exercise regularly, the International Society of Sports Nutrition suggests 1.4 to 2.0 grams per kilogram of body weight a day. Food counts first. Over the long term, protein from eggs, fish, meat, dairy and legumes builds muscle as well as any powder. A powder simply makes the target easier to hit.
Do you need BCAAs?
Probably not. The branched chain amino acids (leucine, isoleucine and valine) are three of the nine essential amino acids, and every serve of protein already contains them. On the current evidence, they add little when your total protein is adequate. A separate BCAA product mostly duplicates what you already have.
When doses stack up
The risk I see most isn't one bad product. It's several reasonable products that overlap.
Vitamin B6 is the clearest example. A healthy adult needs 1.3 to 1.7 mg a day, which a normal diet easily provides. Yet B6 turns up in magnesium, zinc and stress formulas, in multivitamins, in pre workout powders and in energy drinks. Take a few of these together and the total climbs well past what anyone needs. By late 2025, the TGA had received 250 reports of nerve damage linked to B6 products. Numbness or tingling in the hands or feet is the warning sign. On 14 October the TGA opened consultation on clearer B6 labelling, and from 1 June 2027, oral products with more than 50 mg and up to 200 mg per daily dose become Pharmacist Only medicines.
Caffeine stacks the same way, across coffee, pre workouts and energy drinks. So do vitamin D and calcium when a multivitamin sits alongside a separate product.
The fix is simple. Write down everything you take, add up each ingredient across products, and bring the list to your doctor.
Gummies, drinks and sachets: do the new formats work?
Gummies, ready to drink shots and sachets are built for convenience, but convenience is no use if the format doesn't deliver the dose on the label.
Creatine gummies show why it matters. When the supplement maker NOW tested 12 brands, five contained little to no creatine, and the failing products showed signs the creatine had broken down. A separate round of testing by SuppCo found four of six gummies failed, while all five powders met their label claims. Creatine is unstable in warm, moist, acidic products like gummies, where it slowly turns into creatinine, which does nothing for your muscles. Some gummies do pass, but reaching 5 grams usually takes four or five a day.
The lesson applies to any new format. Check the dose of each ingredient per serve, and how many units make up that serve. Be wary of blends that hide individual doses. A new format is only as good as the testing behind it.
How to tell a good product from a bad one
Start with the label. In Australia, most vitamins, minerals and herbal products are legally medicines and carry an AUST number. Which number they carry tells you more than anything on the front of the pack.
Label | What the TGA checks before sale | Typical products |
|---|---|---|
AUST L (listed) | Low risk ingredients, made to Good Manufacturing Practice. Not checked to see if it works. | Most vitamins, minerals and herbal products |
AUST L(A) (assessed listed) | All of the above, plus the evidence for its health claims | A small number of complementary medicines |
AUST R (registered) | A full assessment of quality, safety and efficacy | Prescription and many pharmacy medicines, and a few complementary medicines |
No AUST number | Regulated as a food. No TGA check. | Protein powders and many sports products |
Most shoppers don't know this. In a CHOICE survey, 43% of people who were aware of AUST numbers wrongly believed listed products had been checked to see if they work. Checks after sale are thin too. A July 2026 paper in the Internal Medicine Journal estimated that only about 2% of listed medicines have had their efficacy evidence reviewed. You can look up any AUST number for free on the TGA's ARTG search.
Then look past the label. These are the questions I ask of any product, including the ones I take:
Does it contain the studied ingredient, in the studied form, at the studied dose?
Has the company tested its own finished product in trials, registered them and published the results, including results that disappoint?
Does it test every batch, and will it supply a certificate of analysis on request? For sports products, look for independent batch testing programs such as HASTA or Informed Sport.
Are the claims modest? Be wary of "detox", of "clinically proven" with no trial named, and of anything that promises a result.
Credible brands spend money on evidence their competitors skip, and they're open about what their products can and cannot do. Rewarding them with your custom is how the standard rises.
What I take, and why
Every person is different, which is why the specifics are worth a proper conversation. But since patients ask, here is my short list.
Creatine, to train harder and recover between hard efforts.
Plant protein, to reach my daily protein target. Like most adults of East Asian descent, I'm lactose intolerant, and even whey isolate leaves me bloated.
Vitamin D3, taken with a meal, because I spend most of my day indoors.
I read the full breakdown of everything I take, down to the dose of each ingredient per serve. The brands I use, and recommend to patients, are ones I've chosen after looking into how they're made and what research sits behind them.
Where this leaves you
Start upstream, with whole foods. Then work out what your diet, your blood results, your training and your stage of life say you still need. Take each product the way that makes it work, add up what overlaps, and know what everything in your cupboard is for. A good supplement is a precise tool. A bad one is an expensive habit, and occasionally a harmful one.
If you'd like help sorting through your own bag of bottles, an initial consultation is the starting point.
FAQ
Is vitamin D better taken in the morning?
The timing matters less than taking it with food. Vitamin D is fat soluble, so it absorbs better alongside a meal that contains some fat. Pick whichever meal you'll remember.
Is creatine bad for your kidneys?
In healthy people, research has not found kidney harm at usual doses. Creatine can raise creatinine on a blood test, which can look like a kidney problem when it isn't, so tell your doctor you take it. If you have kidney disease, check with your doctor first.
Can supplements interact with my medicines?
Yes. St John's wort can weaken several medicines, including some contraceptives, and shouldn't be combined with antidepressants. Calcium, iron and magnesium can block the absorption of thyroid medicine and some antibiotics if taken at the same time. High dose fish oil can add to the effect of blood thinners. Bring a full list of what you take to your doctor or pharmacist.
General information, not individual medical advice. Speak to your own doctor.
