Yes, you can. Most vitamins and minerals are low risk at typical supplement doses, but high doses of vitamin A, vitamin E, beta-carotene, vitamin B6, iron and zinc have documented harms.[1][2] The safest approach is to add up what you take, check the label doses, and talk to your GP or pharmacist before starting a high-dose product.
This is general health information. Consult your GP.
Can you take too many vitamins? Yes, supplements can be harmful in excess. In US national survey data, around one in two adults had used at least one dietary supplement in the previous month.[3] Most use products with a modest dose, and it's worth knowing which ones need caution.
A lot of people assume that because vitamins are "natural", extra must be harmless. They can still cause problems when taken in large doses or in combination. Below we cover which supplements carry the most risk, the warning signs to look out for, and the habits that keep supplement use safe. If you're unsure about a product, ask your GP or pharmacist.
Numbers at a glance
Figures are taken directly from the cited sources. Check each source for the population and study design.
Supplement safety in five ideas
Stored, not flushed
Fat-soluble vitamins can build up over time.
Keep out of children's reach
Iron overdose is a leading cause of poisoning in young children.
Check your total
Add up every product you take.
Tell your doctor
Including herbal and sports products.
Food first
Most people don't need megadoses.
Four habits for safer supplements
Press play, or tap any step.
Four habits for safer supplements
1. Add up every product · 2. Tell your GP · 3. Store out of children's reach · 4. Ask before starting high doses
What the animation shows
- 1. Add up every product. Doses stack. A multivitamin, a "hair and skin" product and a sports powder can each contain the same vitamin.
- 2. Tell your GP or pharmacist about every supplement. Vitamins and minerals can interact with medicines, and some affect blood test results.
- 3. Store supplements out of children's reach. Iron tablets in particular are a leading cause of poisoning in young children, so treat them like medicine.[9]
- 4. Ask before starting high doses. Check the label and ask your pharmacist if a product's dose is well above the daily recommended amount.
This is general health information. Consult your GP.
Why fat-soluble vitamins carry more risk
Stored in the body, so levels can build upExtra amounts of water-soluble vitamins are mostly passed out in urine. Fat-soluble vitamins are different. They can stay in body fat and the liver, and because of that, toxicity usually builds up over weeks or months of high intake.[2]
Key point: vitamins A, D, E and K can accumulate over time. Vitamin K is less often a problem. Vitamin A is the best known cause of toxicity.[2]
This is general health information. Consult your GP.
Vitamin A and beta-carotene toxicity
Liver damage, birth defects, and lung cancer risk in smokersToo much vitamin A can be harmful. Long-term excess can cause headache, liver damage and bone thinning, and vitamin A in early pregnancy is linked with birth defects.[4] The US Preventive Services Task Force (USPSTF) notes that moderate doses of vitamin A supplements may reduce bone mineral density, and that high doses may increase the risk of hip fracture.[4]
Beta-carotene is the plant form that the body converts into vitamin A. It's safe in food, but in two large randomised trials of heavy smokers and asbestos-exposed workers, beta-carotene supplements increased the risk of lung cancer.[5] USPSTF recommends against beta-carotene supplements to prevent cardiovascular disease or cancer.
Most important: the USPSTF recommends against beta-carotene supplements, and people who smoke or have been exposed to asbestos should avoid them. If you're pregnant or planning a pregnancy, check any vitamin A supplement with your GP.[4][5]
This is general health information. Consult your GP.
Vitamin E and bleeding risk
Haemorrhagic stroke, blood thinners, and cancer trial findingsTrials have found a higher risk of haemorrhagic stroke (bleeding in the brain) after vitamin E supplementation at high doses.[6] The SELECT trial in men found vitamin E alone was linked with a higher rate of prostate cancer. Vitamin E can also increase bleeding risk, especially in people taking blood thinners such as warfarin.
The dose needed for a clinically important effect isn't known, but it's probably above 400 IU a day.
Use a blood thinner? Tell your GP or pharmacist before taking vitamin E. The same goes for vitamin K, which affects how warfarin works.[6]
This is general health information. Consult your GP.
Too much vitamin D: calcium and kidney stones
Hypercalcaemia from long-term high dosesVitamin D toxicity is rare but real. At high doses it raises calcium in the blood (hypercalcaemia), which can cause nausea, vomiting, weakness, frequent urination and kidney stones.[8] Symptoms often include weakness, tiredness, loss of appetite and constipation.
One trial in older adults found a higher fall rate with a very high yearly vitamin D dose of 500,000 IU (about 12,500 mcg) a year.[8]
Keep it in context: if your GP has prescribed vitamin D for a deficiency, keep taking it as directed. The risk is mostly with high doses taken without a blood test.
This is general health information. Consult your GP.
Vitamin B6 and nerve damage
Numbness, tingling, and the "just a little extra" trapTaking 50 mg a day of vitamin B6 for 12 to 36 months can cause peripheral neuropathy: numbness, tingling or pain in the hands and feet.[7] Symptoms depend on the dose, and some cases were seen at doses below 50 mg a day. Symptoms usually improve when the supplement is stopped, but recovery can be slow.
Separately, cohort data show a link between B6 intake and a higher risk of hip fracture when combined with high B6 and B12 intake.
Watch for: numbness, tingling or weakness in your hands or feet. Stop the supplement and see your GP.[7]
This is general health information. Consult your GP.
Iron and zinc: minerals that can harm
Overload, poisoning, and copper deficiencyIron is useful when you're deficient, and risky when you're not. Excess iron can cause constipation, nausea and stomach pain. Over time it can build up in the body, especially in people with haemochromatosis, a condition that causes the body to store too much iron.[9] It can also affect how other medicines are absorbed.
Too much zinc can cause nausea, vomiting and a metallic taste. Taking 40 mg or more over a long period can lower copper levels, leading to anaemia and nerve problems.[9] Taking 50 mg of zinc daily for months has caused copper deficiency in some people.
Store iron safely: iron tablets should be kept out of reach of children, and kept in the original container. If a child swallows any, call the Poisons Information Centre on 13 11 26 or go to your nearest emergency department.
If you've been told you have low iron, see our guide on Iron Infusion Therapy in Perth.
This is general health information. Consult your GP.
Biotin and blood test results
Can interfere with lab testsThere's no evidence that biotin is harmful at high doses, but it can interfere with laboratory tests that use a biotin-streptavidin technology. This may give falsely high or falsely low results for thyroid hormones, hormones, and cardiac markers such as troponin.[11]
Case reports describe results that wrongly suggested heart attacks or thyroid disease. The US FDA has issued a safety communication about this. Tell the doctor or pathology collector that you take biotin before any blood test.
Before a blood test: tell your GP or pathologist about biotin, including in hair, skin and nail products.[11]
This is general health information. Consult your GP.
Lower-risk vitamins and minerals
Generally well tolerated at usual supplement doses| Nutrient | What the evidence says | Risk |
|---|---|---|
| Vitamin C | Excess is mostly passed in urine. Very high doses (over 2 g a day) can cause diarrhoea and stomach upset, and may raise kidney stone risk.[12] | Low |
| B12 | No upper limit has been set. Excess is generally not harmful and is passed in urine.[12] | Low |
| Vitamin K | Natural vitamin K has little known toxicity, but it affects blood thinners such as warfarin.[12] | Interaction |
| Folate | Safe at usual doses. High doses can hide B12 deficiency.[12] | Moderate |
| Calcium | Supplements can cause constipation and, in high doses, kidney stones. Getting it from food is preferred.[12] | Moderate |
Low risk isn't the same as useful. The USPSTF concluded that evidence is insufficient to recommend multivitamins for preventing cardiovascular disease or cancer in most healthy adults.[1]
This is general health information. Consult your GP.
Warning signs of vitamin toxicity
When to stop the supplement and call your GPStop the supplement and call your GP if you notice any of these while taking vitamins or minerals:
- Numbness, tingling or weakness in your hands or feet (possible vitamin B6 nerve damage)
- Unexplained bruising or bleeding that is out of the ordinary
- Weakness, tiredness, loss of appetite or constipation (possible high calcium from vitamin D)
- Yellowing of the skin or eyes, which can be a sign of a liver problem (high-dose vitamin A)
- Ongoing nausea, vomiting or stomach upset that won't settle
Bring your bottles. Take your supplements, or photos of the labels, to your appointment so your GP can check what you take and how much.
This is general health information. Consult your GP.
The Bottom Line
Most vitamins and minerals are low risk at normal doses, but more isn't better. High doses of vitamin A, vitamin E, beta-carotene, vitamin B6, vitamin D, iron and zinc have documented harms.[1][2] For preventing heart disease or cancer, multivitamins show little benefit, and the evidence for most extra supplements in healthy people is limited.
If you do need a supplement, take the dose you need, add up every product, keep them away from children, and carry your list of supplements to your GP review.
Not sure what you need? A heart health check or a preventive health check with your GP is a good place to start.