Lose The Spoon: Study Finds Milliliters Best For Measuring Kids’ Meds

Veronica Thomas
CommonHealth Intern

You wake up to your 8-year-old son crying in the middle of the night. He’s had a sore throat for a few days, which the pediatrician is treating with liquid Tylenol. As you grab the bottle and kitchen spoon from the medicine cabinet, you wrack your brain trying to remember the doctor’s instructions. Was it two teaspoons or two tablespoons? But wait, the pharmacist had said to measure it in milliliters.

Confusion about medication measurement like this is surprisingly common among parents, often resulting in serious dosing errors that contribute to more than 10,000 calls to poison centers each year and 70,000 ER visits.

Parents who used teaspoons or tablespoons were twice as likely to make a mistake.

A new study in the journal Pediatrics found that around 39 percent of parents incorrectly measured the dose they intended and about 41 percent made an error in measuring what their doctor had prescribed. The researchers found that parents who used teaspoon or tablespoon units for medications were twice as likely to make a mistake in measuring the dose compared to parents who only measured medications in milliliters.

This increased error may partly be due to the fact that parents measuring in teaspoons or tablespoons are more likely to use a kitchen spoon to measure the medication, rather than a standardized instrument like an oral syringe or cup. However, even parents using standardized instruments were more likely to make a dosing mistake if they used teaspoon or tablespoon units. The link between tablespoon or teaspoon use and measurement error was even stronger among parents with low health literacy or limited English proficiency.

To minimize this confusion and reduce medication errors among parents, the study investigators suggest adopting a milliliter-only unit of measurement. But while a standardized unit of measure seems like the logical fix, it probably won’t be a quick one, according to Dr. Shonna Yin, the lead investigator of the study.

She sees growing support for a move towards a standard milliliter system from groups like the American Academy of Pediatrics, the American Academy of Family Physicians and the American Association of Poison Control Centers, but says concerns remain that this transition would cause greater confusion, since parents are familiar with teaspoon and tablespoon terms.

I asked Dr. Yin, from the New York University School of Medicine and Bellevue Hospital Center, to provide additional insight on the study’s implications, including what parents can do to reduce dosing errors. Our conversation, edited:

What is the typical scenario in which dosing error occurs? 

Not a lot is known about the scenarios in which dosing errors occur, as there have been few studies looking at this issue, and many dosing errors are not detected. One contributor to dosing errors is parent confusion related to units of measurement. For a single prescribed medication, different units of measurement, like milliliters, teaspoons and tablespoons, may be used interchangeably as part of dosing instructions when parents are being counseled by their doctor or pharmacist, and when the dose is shown on the prescription or medication bottle label. Seeing and hearing different units of measurement from each source of information can lead to confusion.

In addition, the words teaspoon and tablespoon sound very similar, and the abbreviations for these terms, “tsp” and “tbsp”, are easily confused. Finally, terms like teaspoon and tablespoon inadvertently endorse the use of kitchen spoons, which vary greatly in size and shape, making it difficult for parents to accurately measure their child’s dose of medication. This is why it is recommended that parents use standard dosing devices — like oral syringes, droppers, or dosing spoons — that have markings on them to help parents know how much to dose.

It appears that dosing error is quite common. How often do these errors result in serious illness or death? 

Luckily, dosing errors that result from parent confusion regarding units of measurement usually do not result in serious health consequences. The most serious consequences are likely to result when parents incorrectly dose a medication for multiple doses over a long period of time. Both overdoses and underdoses can be problematic. Overdosing can have serious health impacts on a child, depending on the type of medication involved. For a drug like acetaminophen, there is a potential for liver damage and death. Underdosing can lead to a child’s illness not being properly treated.

What's the next step? Is more research needed before milliliters will become the standardized unit of measurement? 

There is compelling data from this study, as well as from others, that the use of teaspoon and tablespoons for dosing is extremely confusing, and contributes to medication errors. This has led groups like the American Academy of Pediatrics to come out in support of a mL standard. Our study helps provide evidence to support a move to a single standard unit of measurement based on milliliters.

What agency will be responsible for mandating this standard? How will prescribing providers be monitored to ensure compliance? 

The Food and Drug Administration would have a great deal of influence if they mandated this standard, as they have oversight over the labeling of medications. Professional organizations could encourage providers to adhere to recommendations through educational campaigns and through their maintenance of certification processes, but these organizations would not be responsible for monitoring providers.

How long do you think this transition will take? When can we expect to see children’s medications measured in milliliters?

It is likely that the transition to a milliliter standard will take some time, as there are a number of stakeholders involved, including individual health care providers such as doctors and pharmacists, health care systems and pharmacies, manufacturers of medications and dosing devices, as well as pharmacy system software companies and prescribing software companies, including ones associated with electronic health record systems.

From a consumer standpoint, what can parents do with this information to prevent dosing errors? Can they ask the pediatrician or pharmacist to provide the dosage in milliliters and/or ask for standardized measurement instrument?

Parents should not be afraid to ask questions of their health care provider to ensure that they know the correct dose for their child, and can ask for their child’s dose in milliliters. Parents should always use a standardized dosing instrument, like an oral syringe or dosing spoon, to measure their medications. If they don’t have one, they should ask their doctor or pharmacist for one. Parents should never use a kitchen spoon to dose medications.