Welcome back to our weekly diabetes advice column, Ask D’Mine — with your host veteran type 1, diabetes author and educator Wil Dubois. This week, Wil looks at the newest basal insulin to hit the market: Sanofi’s Toujeo (aka the Son of Lantus). It was newly approved by FDA early this year and launched in early April, and it can be a little confusing since the unit-dosing is a bit different from what we’re used to. Don’t worry, Wil’s got this… 

{Have your own questions? Email us at AskDMine@diabetesmine.com}


Matthew, type 2 from Oregon, asks: I’m confused about the new basal insulin Toujeo, I understand that it is U-300 and therefore should be more “concentrated,” but when I went to the webpage for this product, it talked about how Toujeo is a 1:1 dosing and conversion from Lantus. I thought that the dose would actually be less as it’s more concentrated. I also read about how people actually required a higher dose of Toujeo to allow the same blood sugar control as with Lantus. How on earth does this all work?!

Wil@Ask D’Mine answers: It’s fuzzy math, Mathew, but you chose the right person to ask. However, a warning: It’s impossible to give a concentrated answer about concentrated insulin! So OK, let’s concentrate (get it?!)…

Most modern insulins are what we call U-100, which means that there are 100 units of insulin per milliliter of fluid. That’s what they mean by its concentration. Back in the day we also had U-20, U-40, and U-80 insulins. I also had it in my head that there was a U-60 at one time, but I may be wrong about that, as a quick Google search only turns up articles about the German Sub U-60, which apparently had one of the least distinctive war records of the Nazi fleet — and no discussions of insulin.

Anyway, back in the many-concentration days, each insulin had its own syringe. If you got the wrong syringe or the wrong vial from the pharmacy… Well, I’ll leave that to your imagination, but one survey in 1967 found that fully halfof diabetes patients on insulin were making dosing errors due to the overlapping and confusing systems. That ultimately led to the adoption of the single U-100, initially here in the U.S. and Canada and eventually worldwide. See? Once-upon-a-time we Americans were on the leading edge of diabetes care instead of on the trailing edge we often find ourselves on today!

Today, nearly all insulins—be they basal, “N,” fast, rapid, or mix—are U-100.

Except, of course, U-500, the super-concentrated, five-times-more-powerful insulin we have for those who need more than 250 units a day of the conventional stuff. U-500 gives pharmacists fits because they are purists and believe that U-500 should be administered only in tenths and twentieths of an mL in a Tuberculin syringe. While they are technically correct, there’s nothing wrong with the in-the-trenches workaround of just using U-100 syringes and taking 1/5 the dose you would have taken of U-100. Units are technically pure, but patients don’t care.

And now, apparently, Toujeo maker Sanofi doesn’t care either, because they just tore up the Unit Rulebook and threw it away. The reason that Toujeo doses 1:1 (meaning you’d take the same number of “units” that you did before) is that Sanofi has re-defined the unit. Toujeo comes only in a special SoloStar pen that actually delivers 1/3 of a unit with each click. In fact, the 450 “unit” pen actually only holds 1.5 mL of fluid, exactly half the volume of the pens we are used to. Basically, the new pen has been recalibrated to deliver smaller doses. For each single “unit” you click into the pen, you’re actually getting one-third of what you are accustomed to but of a higher potency liquid.

It’s hard to wrap my brain around all the numbers, but I think, in general, this is safer. We have to get away from thinking of a unit as something pure and recognize that it’s nothing more than a reference number, rather than an actual dose.

Now, what about that whole needing more thing? Well, even though Toujeo is nothing more than ple syrup-thick Lantus that’s three times more concentrated, for some reason it doesn’t work three times better. If you were well controlled on, say 100 units of Lantus, taking 100 of the new one-third 100 units of Toujeo won’t control you.

How much more would you need?

Well, I crunched the numbers for you, Matt. Let’s say you needed 100 units of Lantus. If you switched to 100 “units” of the new stuff you’d be getting the volume equivalent of 33.34 units because it’s three times more concentrated. Of course, with this stuff not being as strong as Lantus you’d then need to increase that number, worst case for you as a type 2, by 15%. Looking at it through a U-100 lens, that means you’d need to take a hair over 38 units, a volume reduction of 62 units, or about a 60% reduction in volume. OK, it’s not the 2/3 reduction you’d expect in a U-300 insulin, but it’s not chump change, either.

Of course, if your pen conked out, you’d need to keep your wits about you if you used a U-100 insulin syringe to suck out an emergency dose. Remember the “units” on the Toujeo pen are smoke and mirrors. If you don’t remember that, you’ll give yourself a triple overdose (minus 11-17%).

Some oddball things you need to know: Toujeo is so extended that onset of action is not for six hours, and it can take “at least five days” for the insulin-lowering action to “manifest.” Because of this, doctors are advised not to use the typical daily up-titration to adjust the dosage, but to increase every 3-4 days. A pen is good for 28 days, and can be kept at room temp (if your room is cooler than 86 degrees) during that time. And I’ve read that Sanofi is pricing the new juice at about the same dollar-per-unit as Lantus, but I’m not clear which math they are using: The one that uses less juice for the buck or the one that would be three times higher.

Now, there was much excitement earlier about the fact that Toujeo was supposed to be less hypo-prone, but the labeling doesn’t support that, and that has investors upset. And speaking of investors, why a U-300 at all? It could be because Americans—type 2s and type 1s alike—are getting fatter and fatter. The more you weigh, the more insulin you need. Many PWDs need so much insulin nowadays that the tissues can’t absorb it correctly. The solution is more concentrated insulin. OK, you say, but if we already have U-500, why add another one?

Because, frankly, U-500 ain’t that great. It has a camel-shaped action curve sort of like the old NPH. This means that six to eight hours downstream of a shot, it reaches peak action, giving rise to the risk of lows at odd hours. It’s also only a 12-hour insulin. So there’s certainly a market for a more concentrated 24-hour basal.

Or, people more cynical than I might suspect that Sanofi is freaking out because their cash cow just got sent to the slaughterhouse. Lantus is out of patent and Eli Lilly and company are poised to release generic Lantus to compete, a move delayed only by a strategic lawsuit filed by Sanofi.

Only time will tell if Toujeo is a game-changer like Lantus was when it was first introduced, or if it turns out just to be Lantus repacked in a shiny new patent.


Disclaimer: This is not a medical advice column. We are PWDs freely and openly sharing the wisdom of our collected experiences — our been-there-done-that knowledge from the trenches. But we are not MDs, RNs, NPs, PAs, CDEs, or partridges in pear trees. Bottom line: we are only a small part of your total prescription. You still need the professional advice, treatment, and care of a licensed medical professional.