Those groups of people who may be at particular risk of a lack of iron include teenage girls as they start to have periods; women of child-bearing years as they need a good source to pass on to their growing baby; vegetarians and vegans as they do not eat red meat, and the iron in green vegetables is a lot more difficult for the body to absorb; athletes as they are using more due to being so active.
It is important to get into the habit of taking your supplement at the same time of each day. Choose a time when you will remember easily; for example, many people choose to take their supplement when they are having breakfast.
Multivitamin and mineral supplements are well tolerated by most people. Some of the individual ingredients may have modest effects on the stomach or bowel. These can be minimised by taking the supplement with food. Always remember to take your supplement with a drink in order to help it pass easily into your stomach. Water or juice are the best options.
These are European nutritional recommendations. RDA stands for Recommended Daily Allowance. It is the amount of a nutrient that should, in theory, satisfy the daily needs of nearly all the population of the European Union. Currently only 18 nutrients have RDAs.
You can take too high a level of some vitamins and minerals but this is true of many things including salt, alcohol and even water. All the major vitamins and minerals have established safety levels (see HSIS web site). Water-soluble vitamins are usually very safe whereas some of the fat-soluble vitamins can only be taken safely for long periods of time at levels only 2 or 3 times the Recommended Daily Allowance. This is because excesses of these vitamins are stored in the body and can accumulate.
If you are taking only one supplement there is generally no need to be concerned as manufacturers naturally take these Upper Safe Levels into account. However if you're combining supplements that contain some of the same nutrients, you should exercise some caution. A table indicating Upper Safe Levels of vitamins and minerals can be found on the HSIS web site.