We’ve all seen the adverts and articles designed to hook you in and get you reading, exploiting the human trait of wanting to know and hating the idea of missing out.

Perhaps you even read that as 3 supplements that your doctor doesn’t want you to know about.

In this case, they really do want you to know. These can save your life if you need them, and all it takes is a blood test.

Vitamin D

This is a pre-hormone, one of a group of chemicals called secosteroids that has a huge range of effects on the body. In general, the best form is that made by the skin due to sun exposure but from October to March in the U.K., the UV in sunlight is inadequate and we therefore do not produce enough. Add in cultural and personal modes of dress, indoor work and poor diet and there is a risk of deficiency. If you suffer from increased fatigue in the winter (SAD), a family history of bone problems or darker skin, then a quick blood test at the GP can check for vitamin D levels. Current target levels are between 50ng/L and 75ng/L depending on your local health authorities.

Vitamin B12 / Folic acid

Again, these serve multiple purposes in the body, from the formation of neural tubes in a foetus and nerve conductions generally, to the creation of red blood cells. If you’re feeling under the weather and have a low nutrient dense diet, then, again, a quick blood test can help have a look at this potentially silent sign. If you are low, then they can be brought into line quickly with injections, or high dose supplements, especially B12.

All other supplements are for personal preference. I like adding magnesium and probiotics but these are for researched and otherwise investigated conditions, with medical approval.

As with all things, always seek medical advice before changing or starting a plan.