Why not rather administrate vitamins by injection ? There are both advantages and disadvantages to giving vitamins by injection. This method is normally reserved for animals suffering severe hypovitaminosis or where there has been a toxic interaction which can be reversed by vitamins. Most vitamin injections are designed to be given by the intra-muscular route; rarely are they given intravenously. The main advantages are that the injected vitamins bypass the digestion/absorption route and are 100% effective. They produce a sudden, large surge in the blood contents which may have pharmaco-dynamic effects. The bypassing of the alimentary canal is not particularly important for the water-soluble vitamins which tend to be 100% absorbed anyway. It is much more relevant for the fat-soluble vitamins where the efficiency of absorption is probably only 25%. However there are also disadvantages. In our opinion the risks far outweigh the advantages. The greatest problem of all is sensitisation – either to the vitamin substance or to an adjutant. For example several companies used to have a combined vitamins A, D and E injection. We know they had to deal with several cases of death in horses from anaphylactic shock brought on by sensitisation to one of the ingredients, usually the emulsifier used to ensure that the fat-soluble vitamins could be carried in suspension in the blood plasma. Another difficulty – particularly of single vitamin injections – is that they are given in sufficiently large quantities to unbalance the vitamin/hormone/enzyme system leading to inefficiencies of the other vitamins. The immediate surge in blood contents falls away fairly rapidly; the rate of decay varying between vitamins. This is generally because the homeostatic mechanisms in liver and kidneys remove excess levels and excrete them as rapidly as possible. Within 24 to 48 hours the blood contents will be almost back to where they were before the injection unless steps are taken to renew the injection on a daily basis. We do not like the idea of sticking needles in horses every day, particularly if there is an on-going risk of sensitisation and anaphylactic shock. Equally there is always a risk of septic reactions since few stables practice good asepsis. In conclusion, we strongly advise against the administration of vitamins by injection (except in case of Force Majeur). For example, the effect of 15 injections is lower than a daily dosage of 75 g of TWYDIL® RACING.