Everything you need to know about LactCheck and medication safety during breastfeeding.
RID (Relative Infant Dose) is the percentage of the mother's dose of a medication that reaches the infant through breast milk. An RID below 10% is generally considered compatible with breastfeeding by clinical guidelines.
The M:P ratio (Milk-to-Plasma ratio) compares the concentration of a drug in breast milk to its concentration in the mother's blood. LactCheck provides M:P predictions alongside RID for a more complete picture of drug transfer.
'Verified' means the data comes directly from published clinical lactation studies — researchers measured the drug in actual breast milk samples from nursing mothers. 'Predicted' means our machine learning model estimated the value based on the drug's molecular structure, since no direct clinical study exists for that specific medication.
Our models use honest nested cross-validation to prevent inflated metrics. For RID predictions in the typical clinical range (≤20%), we achieve Spearman ρ = 0.48 (filtered model, n=429). For M:P predictions in the typical range (≤3.0), we achieve Spearman ρ = 0.575 (filtered model, n=239). All predictions include an expected range — the model's uncertainty is transparent, not hidden.
LactCheck has both a free and paid Pro plan. The free plan gives you access to our complete verified drug database — you can look up any drug in our database with their RID and M:P values from clinical studies. The Pro plan adds ML predictions for drugs not yet in the database, drug class rankings, and shareable links.
A low RID doesn't mean the drug is risk-free. RID only measures how much of the mother's dose reaches the baby through milk. A drug with an RID of 2% could still be harmful if it's toxic to infants in small amounts (e.g., some chemotherapy agents, lithium in certain contexts). Conversely, some drugs with higher RID values (like metformin at 6%) are considered clinically safe. Always consider the specific drug, the infant's age and health, and consult your healthcare provider.
Individual pharmacokinetics vary significantly between people. A predicted RID of 6% might actually be 4% in one person and 9% in another.
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