There is no list of lactation risk categories that is uniformly accepted. The “Lactation Risk Category,” developed by Thomas Hale, M.D., is most frequently used:
L1 – SAFEST
o Drug has been taken by a large number of breastfeeding mothers without any observed increase in adverse effects in the infant.
o Controlled studies in breastfeeding women fail to demonstrate a risk to the infant.
L2 – SAFER
Drug has been studied in a limited number of breastfeeding women without an increase in adverse effects in the infant.
L3 – MODERATELY SAFE
There are no controlled studies in breastfeeding women, and the risk of untoward effects to a breastfed infant is possible, or controlled studies show only minimal non-threatening adverse effects.
Drugs should be given only if the potential benefit justifies the potential risk to the infant. ADHD medications fall in this category.
L4 – POSSIBLY HAZARDOUS
There is positive evidence of risk to a breastfed infant. If the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective, use may be acceptable.
L5 – CONTRAINDICATED
Studies in breastfeeding mothers have demonstrated that there is significant and documented risk to the infant. The risk of using the drug in breastfeeding women clearly outweighs any possible benefit from breastfeeding.