Water-soluble vitamins are not stored in the body. The body absorbs what it needs and then usually excretes the excess in your urine. The body needs a continuous supply through a steady daily intake. B vitamins are a class of water-soluble vitamins which play important roles in cell metabolism, converting food into fuel and metabolising fats and proteins. They are important for the nervous system and brain function as well as a healthy liver, hair, skin and eyes, and they also strengthen the immune system.

The fat soluble vitamins are soluble in lipids. These vitamins are usually absorbed in fat globules that travel through the lymphatic system of the small intestines and into the general blood circulation within the body. These fat soluble vitamins are then stored in body tissues.

Like vitamins, minerals are substances found in food that your body needs for growth and health. There are two kinds of minerals - macrominerals and trace minerals. Your body needs just small amounts of trace minerals which include iron, copper, zinc and selenium.

Iron deficiency is the most common nutritional problem in Australia. It slows your body’s production of haemoglobin, which your red blood cells need to pick up oxygen from your lungs and carry it to every cell in your body. If you have a shortage of iron you experience symptoms of anaemia, which include feeling breathless after little exercise, feeling tired, heart palpitations and looking pale.

Macrominerals, also known as major minerals, are essential minerals that the human body requires in relatively large amounts to maintain good health.

There is no specific blood test for macronutrients such as carbohydrates, proteins, and fats because the body does not store these macronutrients in the bloodstream, but rather uses them for energy or storage in the body's tissues. However, there are blood tests that can measure various markers related to macronutrient metabolism and overall nutritional status.