Can you get too much vitamin D?
Too much vitamin D is genuinely harmful, but that risk only arises at blood levels far above the recommended values. Stick to the dose on the packaging, and if you are unsure about your level, have it measured by your GP.
Yes, too much vitamin D can genuinely be harmful, but the risk only arises at blood levels above 750 nmol/L. At that level, too much calcium builds up in the blood, which in serious cases causes life-threatening symptoms. As a precaution, researchers apply a safe upper limit of 250 nmol/L.
The label shows how many IU (international units) or mcg are in each capsule or tablet. Those are the numbers that matter. Choose vitamin D3 (cholecalciferol) or D2 (ergocalciferol): both forms work, and the choice between D2 and D3 makes little difference for most people. Stick to the amount on the packaging and do not exceed 2000 IU per day without consulting a doctor. That limit exists because higher doses taken over a long period can reduce bone density and may put strain on the blood vessels, as animal studies suggest. Whether that risk also applies to humans has not yet been proven, but it is barely taken into account in practice.
More and more people are running into problems because supplements are available without a prescription and come with no dosing advice. Symptoms range from nothing at all to an acute, life-threatening condition. The number of reported poisoning cases has risen sharply worldwide, precisely because of the use of unregulated products without supervision. If you have been taking higher doses for some time, ask your GP to measure your vitamin D level.
That is not the same as saying you should avoid vitamin D. A deficiency affects more than one billion people worldwide. People with low vitamin D levels more often develop cardiovascular disease, infections, autoimmune diseases and certain cancers, but whether this is caused by the vitamin D deficiency has not been proven. More is therefore not better, but too little is not good either.
Based on five claims with PMIDs 18689406, 32255467, 18290725, 34518055 and 28516265. The toxicity threshold and safe upper limit are based on clinical research; the atherosclerosis risk comes from animal research only; the rise in toxicity cases is based on case reports and observational research.
How much vitamin D should you take per day?
For healthy adults under 75, extra vitamin D is probably not necessary. For children, adults aged 75 and over, pregnant women, and people at high risk of diabetes, there are indications that supplementation helps, but discuss this with your doctor.
Do tanning beds give you vitamin D?
A sunbed can raise your vitamin D level, but only if the light also contains UV-B, and most commercial beds emit very little of it. Because sunbeds demonstrably increase the risk of skin cancer, a vitamin D supplement is the safer choice.
Is taking extra vitamin C worthwhile?
Extra vitamin C is of little use for most people. Intensive athletes and people following a carnivore diet do have good reason to supplement, and those who take it daily experience slightly milder cold symptoms on average.
Should I take vitamin B12 supplements as I get older?
Getting older increases the risk of a B12 deficiency, even if you eat healthily. A tablet of 1000 µg per day is safe and restores blood levels effectively; discuss this with your doctor. In addition to your B12 blood value, ask for your methylmalonic acid (MMA) level to be measured for a reliable picture.
Does vitamin D help your immune system, or is that overrated?
Vitamin D genuinely helps your immune system, but the benefit of taking extra only really applies if you are deficient. If your level is already good, you have little to gain from higher doses.
How do I know whether I have enough vitamin D, and should I be supplementing?
A blood test (25-hydroxyvitamin D) tells you whether you have a deficiency. At a value below 20 ng/mL, supplementing is worthwhile, particularly for your bones. For your heart, vitamin D has no proven effect.