If you are taking a dietary supplement without a prescription, carefully read and follow any precautions on the label. For these supplements, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to medicines in this group or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Children may be especially sensitive to the effects of vitamin K, especially menadiol or high doses of phytonadione. This may increase the chance of side effects during treatment. Newborns, especially premature babies, may be more sensitive to these effects than older children.
Many medicines have not been tested in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information about the use of vitamin K in the elderly.
Vitamin K has not been reported to cause birth defects or other problems in humans. However, the use of vitamin K supplements during pregnancy is not recommended because it has been reported to cause jaundice and other problems in the baby.
Vitamin K taken by the mother has not been reported to cause problems in nursing babies. You should check with your doctor if you are giving your baby an unfortified formula. In that case, the baby must get the vitamins needed some other way.
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other Medical Problems
The presence of other medical problems may affect the use of dietary supplements in this class. Make sure you tell your doctor if you have any other medical problems, especially:
- Cystic fibrosis or other diseases affecting the pancreas or
- Diarrhea (prolonged) or
- Gallbladder disease or
- Intestinal problems—These conditions may interfere with absorption of vitamin K into the body when it is taken by mouth; higher doses may be needed, or the medicine may have to be injected.
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency—The chance of side effects may be increased, especially with menadiol.
- Liver disease—The chance of unwanted effects may be increased.