Let’s Talk About “Units” — and Why They’re Not What You Think

Written by: James Lydia Lynde

Let’s Talk About “Units” — and Why They’re Not What You Think

Ever wonder what a “unit” actually means when it comes to medication or peptides? It's a question that often leaves people scratching their heads, especially when trying to figure out how much of a substance they're actually getting. Let's dive into the history and meaning of "units" in medication, and why they can be confusing—especially when compared to more familiar measurements like milligrams or milliliters.

The word unit sounds straightforward—but in medicine, it’s anything but. It doesn’t refer to a set volume (like a milliliter) or a weight (like a milligram). It’s a measurement of biological activity, originally developed when medications couldn’t easily be measured by weight alone.

So Where Did “Units” Come From?

The term was first widely used with insulin, which couldn’t be easily weighed in the early 20th century. Researchers had to determine how much insulin it took to lower blood sugar in animals, then base dosing on that effect. One “unit” of insulin became the amount needed to drop a rabbit’s blood sugar to a specific level. This made it easier to compare and prescribe insulin consistently, even if different batches had slight variations in concentration.

Since then, “units” have been used for other medications where potency or biological activity is more important than volume or mass. But that’s also where the confusion starts.

A Unit Is NOT a Universal Quantity

Let’s make this super clear:

A unit is not a fixed amount of medication. A "unit" doesn't tell you the actual amount of medication in milligrams or grams. Instead, it tells you the biological effect of that medication. This means that the same number of units could contain different amounts of the active ingredient depending on how the solution is prepared. Now what happened to have unit be a measurement on an insulin syringe? Way back they determined the amount of the Insulin that caused the desired biological activity - and then just called that a "unit" - and it became common use and is frequently used when referring to an amount of liquid to be injected.

In fact, the same number of units can mean very different actual amounts of substance depending on the concentration of the solution you’re using.

For example:

One peptide product might have 10 mg of a compound reconstituted into 1 mL of liquid.

Another bottle might have the same 10 mg dissolved into 2 mL of liquid.

If you draw up 10 units from each bottle, you’ll get:

From the first: 1 mg

From the second: 0.5 mg

Same number of units. Very different dose.

Think of It Like Baking

Here’s a simple kitchen analogy:

Imagine two jars of vanilla extract. One is regular strength; the other is diluted. You add 1 teaspoon to a cake recipe—but the flavor will be way stronger from the full-strength extract than from the diluted one.

In this case, the teaspoon is like your unit. The volume is the same, but the potency inside that spoon differs depending on how concentrated the vanilla is.

How about another baking example:

If a recipe calls for "1 cup of flour," the amount of flour you actually use depends on how tightly you pack it into the measuring cup.

If you lightly scoop the flour, you might get 120 grams, but if you press it down firmly, you could get 150 grams—even though you're still measuring "1 cup."

Similarly, a "unit" of a peptide or medication could contain different amounts of the active ingredient depending on the concentration of the solution.

Let's use another cooking analogy to make this even clearer.

Imagine you're making a salad dressing, and the recipe calls for "1 teaspoon of vinegar."

Now, if you dilute that teaspoon with water, you might have 5 milliliters of liquid, but only a small fraction of it is actually vinegar.

If you make a stronger version of the same dressing, the same teaspoon of vinegar might be concentrated into just 1 milliliter of liquid. In both cases, you're adding "1 teaspoon of vinegar," but the amount of liquid (and the strength of the dressing) is different.

The same idea applies to medications measured in units. For example:

Insulin: 1 unit of insulin is standardized, so you know exactly how much active insulin you're getting.

Other Peptides or Hormones: If a vial label says it contains "100 units" of a peptide, but one vial is more concentrated than another, the actual amount of peptide in milligrams could be different. For example, a 5 mg vial of a peptide might be labeled as "100 units, (so1 mg would be equivalent to 20 units)" while another 5 mg vial of the same peptide might be labeled as "50 units" if it's more concentrated, and thus 1 mg would be equivalent to 10 units).

Why This Matters

Understanding that "units" don't directly translate to milligrams or milliliters is crucial because it affects how you dose and administer medications. If you're using a peptide or hormone that's measured in units, you need to know the concentration of the solution to determine the correct dose.

For example:

If you have a vial that says "100 units per 10 mL," then 1 mL contains 10 units.

If another vial says "100 units per 5 mL," then 1 mL contains 20 units.

In both cases, you're dealing with "units," but the amount of medication per milliliter is different. THEREFORE TELLING SOMEONE THE AMOUNT OF A PEPTIDE DOSE IN UNITS IS USELESS IN DETERMINING THE AMOUNT OF THE PEPTIDE. More information is needed. No patient/person/researcher/healthcare professional, etc. should be describing a dose of a peptide (except insulin) by the use of the term "units"

So What’s the Takeaway?

Units measure biological activity, not weight or volume (well EXCEPT that the liquid measurement of insulin ended up becoming common vernacular for the amount of liquid in an insulin syringe). They tell you the effect of the medication, not the exact amount in milligrams or milliliters.

The same number of units can contain different amounts of medication depending on the concentration of the solution.

Always know the concentration of the product you’re using.

Don’t assume that “X units” means the same across the board. It doesn’t.

When you’re using peptides, reconstituted medications, or anything dosed in units (except standardized ones like insulin), your actual dose depends on how the product was mixed.

And if someone says “take 10 units” without knowing the concentration—it’s like someone telling you to add “a spoonful of salt” without saying whether it’s a teaspoon or a tablespoon. You could easily overdo it (or underdo it).

So next time you see "units" on a medication label, remember it's not about the size of the cup, but what's in it that counts! Stay informed and always double-check your doses.

Understanding units takes a little extra effort, but it makes a big difference when it comes to safety and effectiveness. If in doubt, slow down, ask questions, and do the math—or better yet, le

arn how to do your own conversions with confidence. 🍳💉

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