Medicine and the Metric System: Part 1

Note: If you care about metric system adoption, you really want to check out my post (10-12-22…National Metric Week) which includes my request to the U.S. House Subcommittee on Science, Space, & Technology for a hearing on the subject. You can see the 10-page report I submitted to Congress:

Now the post begins:

Allow me to present my main point upfront: we are endangering our health by not adopting the metric system in this country.

Prescriptions are written in metric units. Conversions (and possible errors) are made at the pharmacy.

Doctors write prescriptions in metric units. Conversions (and potential errors) are made at the pharmacy.

Let me offer up a couple of examples that hopefully makes this clear. It’s important to understand that the medical field depends on metric units (as does most of science, for that matter). If healthcare workers talk in metric units and the public at large relies on U.S. customary units there is bound to be confusion and misunderstandings. That’s best avoided where your health is concerned since the consequences could be dire.

Metric unit dosing is more precise

Last year Pediatrics (Official Journal of the American Academy of Pediatrics) published an article called “Unit of Measurement Used and Parent Medication Dosing Errors.”1 One of the article’s bottom lines:

Parents who used milliliter-only unit made fewer dosing errors than those who used teaspoon or tablespoon units. Moving to a milliliter-only standard could reduce confusion and decrease medication errors, especially for parents with low health literacy and non-English speakers.

While a minor mistake (whether too much or too little medication) might not make a huge difference for an otherwise healthy adult, these errors can be magnified for babies or those whose health is already compromised.

Most of our teaspoons and tablespoons are meant for eating, not dosing

No on should use "silverware" as substitutes for measuring teaspoons and tablespoons for medicine to avoid dosing errors.

No on should use “silverware” as substitutes for measuring teaspoons and tablespoons for medicine if they want to avoid dosing errors.

Another issue brought up in the piece was that the use of teaspoon and tablespoon employed for liquid medicines “may endorse kitchen spoon use.” I don’t know about you, but I have three sets of measuring spoons and many more spoons that I use for eating commonly referred to as “teaspoons” and “tablespoons.” The problem is, it’s the eating spoons that are often used to measure medicines. (Yes, I used to do that too, without even thinking about it.) If you have a dosing cup with only milliliters, the potential for confusion is greatly reduced.

As if that’s not bad enough

Even your actual measuring spoons aren’t as precise as you think they are. At one point I came across information indicating that up to a 20 percent variance is allowed. Again, that 20 percent could cause dosing errors. In researching this article I came across a page called “Cooking for Engineers” with the post:

I’ve got three sets of measuring spoons, and their measurements differ from each other, up to 1/4 teaspoon! Is there a way to know which (if any), are accurate?

The suggestions that followed involved scales and the temperature at which one should measure the water used to determine volume. Too bad no one suggested going metric.

Additional endorsement of the metric system for health reasons

I also have a document from the Institute for Safe Medication Practices (ISMP) called 2014-15 Targeted Medication Safety Best Practices for Hospitals2 . Two of its best practices mention the sole use of metric system units.

Best Practice 3: Measure and express patient weights in metric units only.

The rationale:

Significant medication errors have occurred when the patients’ weight is documented in non-metric units of measure (e.g., pounds) and it has been confused with kilograms (or grams). Numerous mistakes have been reported when practitioners convert weights from one measurement system to another, or weigh a patient in pounds but accidently document the value as kilograms in the medical record, resulting in more than a two-fold error.

Best Practice 5: Purchase oral liquid dosing devices (oral syringes/cups/droppers) that only display the metric scale.

ISMP has received more than 50 reports of mix-ups between milliliter (mL) and household measures such as drops and teaspoonfuls, some leading to injuries requiring hospitalization.

Beware of teaspoon and tablespoon instructions on prescriptions

Almost uniformly, prescriptions are written in metric units. However, if you pick up a liquid prescription and the dose on the bottle is not metric (and in reads teaspoon and tablespoons), the pharmacy has had to make a conversion. Where there are conversions, there is the potential for mistakes.

In addition, one of the top six recommendations in the 15th annual report of the National Coordinating Council for Medication Error Reporting and Prevention3 includes a “Statement of support for use of the metric system to dose medications.”

Advocate for the metric system and help make the country a healthy place!

Note: Don’t miss my exciting follow-up on this post: Medicine and the Metric System: Part 2



Notes: The article itself requires a subscription However, a summary is located here:

37 thoughts on “Medicine and the Metric System: Part 1

  1. Is the United Kingdom, it is normal to include a calibrated plastic measuring spoon or cup with medicines. Is this not normal in the US?

    • Sometimes metric cups are included, but most other times they are not. We, in America, grew up with common kitchen spoons delivering our medicine doses, and it is so much a part of our culture that it is difficult for many here to get out of their heads.

      Even more tho the point, most of my fellow Americans have an arrogant stubbornness about change. They would rather the rest of the world change to meet U.S. standards, regardless of how foolish the notion is.

      Much of the attitude portrayed in films about the American attitude is very true about a large part of our population. Notice that in movies about aliens from outer space, that they always land in the U.S. and want to talk with the President of the United States. In the film, “Independence Day,” although ships were all over the world, it was the U.S. that saved the planet.

      I worked for a mega church about ten years ago. During a meeting, the senior pastor looked over at my computer and saw that I was calculating stage diagrams using the metric system. He asked me, out loud, “Why are you using metric? What are you, a communist or something?” Everyone in the room responded by laughing quite heartily.

      I have told friends that I am studying to become a Metric Specialist with the USMA, and I have shared how much more pleasant metric is to use. Several of them have said that they don’t care and that they would die before learning metric because it’s stupid and it “just ain’t American.”

      I believe that is the major obstacle to the U.S. switching entirely to S.I.. They will say that it would be too expensive and that too many changes would have to be made, but the truth is that they think it’s un-American and would rather risk the health and safety of others than to concede to cooperating with the rest of the world.

      The other complaint about it is that “it’s just too confusing.” This should come as no surprise from a country that has the lowest math and science scores out of all industrialized countries.

      • I absolutely agree 100% My friends and family always ask me with a snarky tone “Why do you use metric?” I try to explain it to them how easy it is and how the rest of the planet uses it, and their usual response is “We’re not the rest of the world”, instead of them being willing to learn what is simple common knowledge, they’d rather have measurements “translated” over to Pig Latin units as I like to call USC. For instance the other day I told my cousin that drinking plenty of water is important for your health and that you should drink 4 L of water a day (3,700 mL to be exact but we can round) and I used an example of drinking two 2 L bottles of soda but with water, and she insisted that I convert it to ounces. It’s really a petty notion that people in America have, I feel like a black sheep when I use the metric system day to day in a country that still measures things as they did in the 18th century.

      • It could be argued that low math, and especially science scores are BECAUSE of our country’s refusal to adopt the metric standard. If metric units were part of our day-to-day life, it would be more natural for young scientists to study in a field that uses those units. Instead, they are saddled with learning a “new” system of measurement along with learning the subject material, which complicates the learning further. I would argue that this puts our students of science at a greater disadvantage than students of other countries, and whose metric vocabulary is part of their day to day life.

        As far as metric being “un-American,” I’ve heard that too many times to count. It’s sad that pride can be such an obstacle to reasonable thought. Besides, the archaic units we claim as “American” are essentially from England. I thought we got our independence years ago. Why must we cling to their old systems?

      • Metroc system is the heart of medicine. ml that is a very good one for when my son is sick. I believe. yes the metric system should be in affect. you should have ti use it. adding and subtracting is very much a part of metric system. In medicine their us no room for mistakes.

    • I grew up in New York and now at 42 live in Florida I have 3 children and our youngest 10 has Cystic Fibrosis so I’m consistently getting medicine and always since my first son in 1994 have I always received a cup or syringe with any liquid medication even for myself and I have 3 different pharmacy’s I’ve used.

  2. Pingback: Odds and Ends…and the Metric System | More Than A Mile Behind: America and the Metric System

  3. Pingback: Conversion errors and the metric system | More Than A Mile Behind: America and the Metric System

  4. Pingback: Measures and mistakes due to our lack of the metric system | More Than A Mile Behind: America and the Metric System

  5. American or not people are falling behind because the government believes it to be more important to teach things that do not matter in the real world. We should be learning about growing our own food versus fatting everyone else’s pockets. We should be learning about the importance of credit way before we ever establish any. We should be learning how to build together versus working against each other.

  6. I truly and strongly agree with this article and its writer. To little is being done to advance the us in the health care system. Especially for the people hew have learning disabilities and are raising a family. If it was a stander practice to use metric system for dosages the people should be well informed by the heAlth provider to insure the proper treatment is followed for safety and well being.

  7. Yes thank you we may need the metric system for some things and tsps tsps and for some things which works best for dosage.I don’t know because yes you have to get correct dosage and use one that Is most accurate.

  8. All silverware Is made differently In shapes and sizes I’ve noticed that.You would have to use the metric system for correct dosage of medication.How do you know how much to use and what is to much.

  9. When my son was preparing for an army fitness test, he ran with bottles of water in his backpack. The “bottles” were 2L soda bttles. Each bottle weighed 2 kg. What a simple convesion, especially when the British Army works in metric units (I don’t know about the US army, but all the other NATO countries also work in metric units).

  10. This is a very interesting column on the metric system. It makes a lot of sense. I feel as though when it comes to medicine and the health field that its a good thing that metric system was invented. Its important to have the correct amount/ dosage of the medicine needed for one person. Without the metric system I think that it would be a higher rate of drug use. because people would over use or over fill the medicines.

  11. Habit is hard to change. I don’t mind using metric measurements it is just a matter of changing my habits. After reading the information I feel obligated to use metric measurements when dispensing medication to my grandchildren for safety sake. I pray that more parents, grandparents and caregivers see the benefit for their loved ones and choose to do what is in the best interest of “the patient”.

  12. Let us assume that the Germans created a specialised drug that they wish to market world-wide. What language would they use in their instructions for use? The European languages would probably be English, French and German. Over half the people in the European Union can understand English although only about one sixth of the population use imperial units as their preferred system of units. The result is that or use within the EU they would always use metric units – typically “Use x mg per kg body mass”. If they then wish to export the drug to Australia, India or Africa they can use the same instructions – all such countries use metric units and either English or French. It is only when exporting to the US that there might be a problem – not with the language, but with the units of measurement.

    If the drug were first developed in the United States, they would need to use metric units the moment they started to export the product, otherwise the relevant health and safety boards in any the destination countries would probably not permit the drug to be imported into their countries.

  13. Pingback: Medicine and the Metric System, Part 2 | More Than A Mile Behind: America and the Metric System

  14. My kitchen is not the only one that utilizes the metric units. I use it in my everyday living. Dosage should be measured always.

  15. Thank you so much for explain how much of a big difference it is to use metric units then spoons. And you are so right you can’t go wrong using milliliters in doing meds.

  16. Itilla Avent on December 4, 2019 at 9:23pm said I, currently use it when administering medications to my clients with a dosage cup. I, also assist one of my clients by way of taking his insulin , by way of injection with a needle and understand how important to give the precise dosage.

  17. The fun with dealing with mathamatics is very sucessful mental to have, being able to solve problem through mathamatical expressions, measurement, time, is outstanding. 1: 1.6 style.

  18. thanks i learn so much for this Article. I think is best to use metric system is so much easy to measuring system base on the meter liter,and gram as units of length, capacity and weight of the weight mass.

  19. I agree totally… Us as Americans have a lot of pride along with the government. If we have to use money to change anything we are not doing so … The people that are definitely loosing are our children. Yes we are behind in the most two areas: Math and Science…
    I have used my actual kitchen spoon to measure out my kids medicine very frequently until I asked the pharmacist can I please get the correct dosage spoon for my daughter… I only found out because of my saughter’s doctor informed me that they were different….. Change must occur

  20. The metric system is not confusing. One litre is the same whether I am in the United Kingdom (where I live), South Africa (where I was brought up), Germany (where I have worked) and Hong Kong and Australia (where I have been on holiday). The gallon is the confusing unit of measure. I was taught that there were 20 fluid ounces in a gallon, but American texts books assert that there are 16. That is confusing. If you look a little deeper, you will see that the Americans use the “Queen Anne” gallon which dates from 1707 while the Brits used to use the Imperial gallon (which dates from 1824).

    When the US constitution was written, Congress was authorised to declare what units of measure should be used. They failed, so when the US Customs and Excise had to decide which gallon to use, they chose the smallest one in common use , so that they could con the American public into paying more taxes and the American public are still buying that con.

  21. The metric system is a great way to measure any and everything in human life form. The metric system can become confusing at times when the pharmacy have to put the medicine in liquid formation using spoons to take to doses that is needed to treat the client’s issues.

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