Use of Radioisotopes (and other imaging agents) during Lactation

redcrossBy Kelly Bonyata, IBCLC

Radiocontrast dyes (contrast media used with diagnostic testing)

X-rays, MRIs, CAT scans, Intravenous Pyelogram (IVP), ultrasound, mammograms, etc. do NOT affect breastfeeding or breastmilk.

Barium is sometimes used as a contrast agent; it is not absorbed orally and thus does not affect breastfeeding.

Sometimes radiocontrast (contrast) dyes are used to aid the imaging – these dyes do NOT require that mom interrupt breastfeeding.

More on contrast dyes:

“Traditionally, lactating women receiving intravascular gadolinium or iodinated contrast (as opposed to radiolabeled iodine) are advised to discontinue nursing for 24 hours. However, a minimal amount (0.04%) of the intravenous dose reaches human milk, and, of that, less than 1% to 2% is absorbed by the infant. Therefore, breastfeeding can be continued without interruption after the use of iodinated contrast or gadolinium.”

“Because of the very small percentage of iodinated contrast medium that is excreted into the breast milk and absorbed by the infant’s gut, we believe that the available data suggest that it is safe for the mother and infant to continue breast-feeding after receiving such an agent.”

“Because of the very small percentage of gadolinium-based contrast medium that is excreted into the breast milk and absorbed by the infant’s gut, we believe that the available data suggest that it is safe for the mother and infant to continue breast-feeding after receiving such an agent.”

“It seems to be safe to continue breast-feeding immediately after receiving iodinated contrast or gadolinium.”

  • From: Ito S. Drug therapy for breast-feeding women. N Engl J Med. Jul 13, 2000;343(2):118-26. See particularly “Iodine-Containing Contrast Medium and Antiseptic Agents” on p. 123-124.

“Contrast medium is not appreciably deionated. In addition, the absorption of hydrophilic contrast medium is minimal when it is given orally for imaging studies of the gastrointestinal tract. Since no toxicity is known in full-term infants even after the direct administration of contrast medium, the use of these compounds by breastfeeding women appear to pose no risk to their infants.”


Contrast dyes & radiopaque agents
Generic name Trade Name Pregnancy Risk Category** Lactation Risk Category**
Barium Sulfate Barocet… Possibly Hazardous L1
Diatrizoate Angiovist… D L2
Fluorescein Ophthifluor… C (topical), X (parenteral) L3
Gadopentetate Dimeglumine Gadolinium… C L2
Iohexol Omnipaque… D L2
Iopanoic acid Telepaque… D L2
Metrizamide Amipaque D L2
Metrizoate Isopaque… D L2
** Hale TW. Medications and Mothers Milk. 15th Edition. Amarillo, Texas: Hale Publishing; 2012. (More radiocontrast agents are listed in Hale’s book.)

 Lactation Risk Categories  Pregnancy Risk Categories
  • L1 (safest)
  • L2 (safer)
  • L3 (moderately safe)
  • L4 (possibly hazardous)
  • L5 (contraindicated)
  • A (controlled studies show no risk)
  • B (no evidence of risk in humans)
  • C (risk cannot be ruled out)
  • D (positive evidence of risk)
  • X (contraindicated in pregnancy)
NR: Not Reviewed. This drug has not yet been reviewed by Hale.


More information

References (most recent listed first)


Use of radioisotopes sometimes requires temporary weaning. The length of time will depend upon the type of radioactive material used, the dose, the age of the baby, whether baby is getting anything other than breastmilk, and how often mom expresses milk. If use of a particular radioisotope requires that you wean temporarily (some don’t), you’ll want to pump regularly while the radiation is working out of your system to reduce radiation exposure to breast tissue. At least 97% of the radioactivity is gone from your body in 5 half-lives – after this point it is generally considered safe to breastfeed (but other factors may also need to be considered). The more often you pump, the more quickly the radioactivity will be eliminated from your body. It may be possible to have your milk tested for radioactivity, perhaps by the radiology department at the hospital, to help determine when it is safe to return to breastfeeding.

Important note: If you do suspend breastfeeding due to use of radioactive isotopes, it is important to pump regularly during this time. See also Maintaining milk supply when baby is not nursing. You do not need to dump this milk. It can be dated, frozen and used after 5+ half-lives of the radioisotope have passed (after 5 half-lives, 96.9% of the radiation is gone; after 10 half-lives, 99.9% of the radiation is gone). You may also get your milk checked for radiation by your radiology/nuclear medicine department.

Specifics on certain tests

Always check with your nuclear medicine department to find out exactly which radioisotope will be used. Once you have this information, you can look it up in the US Nuclear Regulatory Commission table and other references.

HIDA/Hepatobiliary scan (for gall bladder problems) – This test usually uses Tc-99m-Choletec or Hepatolite, which should not require an interruption of breastfeeding for doses of 4mCi or less; or Tc-99m-DISIDA, which should not require an interruption of breastfeeding (see the links below for detailed information).

Bone Scan – This test usually uses Tc99m-DP or -HDP, which should not require an interruption of breastfeeding for doses of 30 mCi or less (see the links below for detailed information).

Thyroid Scan or Treatment – see Breastfeeding and Thyroid Problems: Diagnostic Testing & Treatments

More information & references

For the most up-to-date specifics on different radioactive agents, see the latest edition of Medications and Mother’s Milk by Thomas Hale, and/or the LactMed online database, maintained by the National Library of Medicine. Breastfeeding helplines are another way to gather information, including the InfantRisk Center Helpline – (806) 352-2519, which is dedicated to providing up-to-date evidence-based information on the use of medications during pregnancy and breastfeeding.

Radiation Workers

Do you work around radiation? It’s important to minimize your risk of inhaling or ingesting any radioactive materials. These links may be helpful to you:

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