What’s the difference between Levemir and Lantus? (Long-acting insulin questions for my friend and her son)

I’m trying to get my friend here so that she can get information on Lantus, Levemir, and everything else MDI. She’s looking for information, but she’s looking in the wrong place. (Clearly the 670G users are a pretty confused group). :rofl:

Her son was using the 670G up until recently but has switched over to Dexcom. It sounds like, as of this morning, he’s also gone back to MDI. They went onto Lantus, which was just over a year old, and found he struggled getting his BGs down below 140. She wonders whether or not that year old status could be the cause? (And I don’t think so, but I’d rather have her hear it from you all). They then switched to Levemir and saw an immediate drop to a 95ish. Her question in my group was is there a difference between Lantus and Levemir and is there a possibility one works better than the other? Also, is there a chance the Lantus had weakened over the year?

I do not know what the doses were or the timing, and I immediately thought maybe there were gaps between the doses that could’ve let him rise. Having just gone through a couple of transitions onto MDI, it has become clear to me that having good timing and an appropriate dosage is imperative to good control.

I’d love to listen to this conversation should it take off. I’m sure I’ll be back on injections soon enough.


@Nickyghaleb, does she let her endo do the dosing for her son, or does she know how to find it out on her own?

Levemir lasts much less for some people. But, if her son is flat at any level (even at 140), then it means that the basal is good. Then he needs to lower himself down with bolus. After that he will be flat again with whatever basal he has figured out keeps him flat for that day or that week. So what she is saying is weird: both Lantus and Levemir need to make him flat, not go to a BG level. Maybe she does not know how to develop a basal?

Do you know how old he is? If he is my age he can PM me and I can explain to him how to figure out his basal.


My son is the one Nicky is referring to. He switched back to MDI on Sat from 670G MM. He is currently using Dex 6G as his CGM. I did contact his Endo prior to making the change and had his full support with dosages to go to MDI and back to the pump if my son decided to do so. He is suppose to take 13 units of Lantus at bedtime and then a carb ration of 1/30 with humalog. We have had the Lantus in the fridge as emergency back up in case of pump failure since Feb of 2017. He ran higher than usual with an average of 140 for both nights. We also did a lot more corrections in those two days than normal. We got a new prescription of Levemir pens yesterday. (Mostly due to the ease of using the pen and a much shorter needle.) Within the first hour of usage he dropped to his normal resting number of 90-95. He stayed there all night. Beautiful. My question was more about Lantus’s shelf life degrading or if people have had a better success rate with Levemir? One or the other is at play. Thank you for sharing your wisdom!

Levemir is a newer basal insulin than Lantus and a better formula from my perspective. It is less likely to cause sudden drops after injection or in the middle of the night, and works consistently at every injection. Most people do not find it lasts as long as Lantus, so it isn’t an insulin you can take once a day. However, most people only get ~20 hours out of Lantus anyway, so it isn’t really a once a day insulin for most people either. The beauty of Levemir is you can get it to last ~12 hours on smaller doses, and then take it in the morning and at night without overlap. This allows you to take different doses for day and night, and to make adjustments every 12 hours more like a pump. For example, I take more in the morning when I anticipate a stressful work day and less on weekend mornings when I’m using Levemir. It’s also less likely to cause lows during exercise compared to Lantus.


According to this article, Lantus that is unopened should be discarded after 28 days if it’s not refrigerated. IT lasts a year in the fridge according to the manufacture if it hasn’t been opened.

However, there have been some studies suggesting that these things are good for much longer. For instance the US government has stockpiles of various drugs that it keeps long past the expiration date, as they’ve done private studies suggesting they’re much more robust. But I think once you go past the expiry you wind up in the “your mileage may vary” camp where most vials are probably perfectly fine but a few odd ones here or there start to go bad. I wouldn’t think it’s out of the realm of possibility that the Lantus went bad.

That said, I tend to question lots of other things before I jump to the “insulin went bad” conclusion. Usually it’s much more likely to be something in my son’s body that I can’t see.

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also that carb ratio seems so high! My son is 5, takes about 8 units of insulin total per day, and his carb ratios during the day vary from 1:28 to 1:20. I know everyone’s different but if I had to guess I would suspect that the carb ratios or ISF are too weak?

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I’m currently using Levemir, after using Lantus for about 10 years. I take the Levemir 2x daily, since it doesn’t last a full 24 hours. I like Levemir better. I found the Lantus to be more inconsistent, from day to day, with more overnight hypos. Bear in mind, this was me non-scientifically comparing Levemir with Lantus in the rearview mirror - I didn’t do side by side testing.

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Thanks, but that has been his carb ratio for a while now. It is actually up from 1/55. At one point he while he was on the pump, last winter, he was using a total of 8 units of humalog per day. His numbers have been great all day today without a need for a correction with the (new) Levemir. His average blood sugar today is 114. He was only DX last summer and is currently in a clinical trial to preserve the Honeymoon Phase.


oh wow! Okay yeah that makes more sense. Our son was diagnosed a few years ago, but he barely had a honeymoon. :frowning: I hope the trial is successful!!!

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This probably means that the 13U estimate was too low for Lantus.

Theoretically, as @TiaG wrote, you might be reaching the end of the guaranteed Lantus life, but, in my experience, insulin hardly ever goes bad: it is the hypothesis of last resort :slight_smile:

I don’t think there is much of a difference between the two except for the likely duration, which is probably much shorter for Levemir for your son. For my son, Lantus works well for 24 hours solid, and Levemir quite a bit less, but they both keep him nice and flat.

You have to be careful when looking at numbers for basal! The only function of basal is to keep you flat. Numbers are somewhat meaningless in that context. A good basal is one that keeps you flat at 60, at 90, or at 150: a bolus or a quantity of carbs will move this nice flat curve up or down. So the level itself is not what will make a basal insulin dosage good or bad for you, it is whether or not it keeps you flat that counts. The dosage of Levemir kept your son flat, so it was a good dosage. The dosage of Lantus didn’t so it probably was not an appropriate amount.

Imho, @Kaelan is right: once you work out the Lantus dosage, they will both work fine for you, with the difference that Lantus will possibly last a full 24 hours. The fact that you got an average of 140 with Lantus with many corrections is likely due to the fact that you were fighting a constantly rising BG because of too low a dose of Lantus. The dosage suggested by your endo is only a first approximation, typically on the low end of the quantity so as to make sure the patient won’t go low, and needs to be adjusted until it keeps your son’s BG flat.

If Lantus lasts 24 hours for your son, that is the one I would recommend: to me, it is a lot easier to deal with regular 24 hour basal injection when that it possible. But, as always, YDMV :slight_smile:


For many folks, Lantus does not last the full 24 hours (it lasts about 20 for me), necessitating either two shots or producing uneven coverage. One other issue with Lantus is that it uses a different mechanism—it forms crystals in the body due to a pH differential to slow release. It seems like for some people, this process is inconsistent, and it can also get disrupted if an injection accidentally lands in the wrong type of tissue, resulting is inconsistent absorption patterns day to day. So for many folks, Lantus is great, but some others really don’t have great results with it. Levemir seems to be much more consistent across people. I know my endo prefers it and wanted me to switch when I was still on Lantus, but turns out I’m a weirdo who gets injection site reactions to Levemir (along with some other insulins; I suspect part of my mast cell activation disorder), so I didn’t. (I’m on Tresiba now, which I vastly prefer to Lantus, although I still kind of wish I’d been able to take Levemir for the ease of shifting my basal dose more readily at times, as has been mentioned.)


I recommend tresiba also, although If the levemir is working fine, maybe just leave it… i used to split the doses morning and night for both levemir and lantus, and to me, they both felt like relabled nph, he may not notice the 6 hour drops, or they may coincide with His lunch, dinner, or snacks, but I would definitely be on High alert every 6 hours, especially if he’s fasting… I also agree that the lantus was probably expired or lost its potency because of its age…

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I don’t think this is typical for most people. Levemir has a slight peak but it’s nothing like NPH.

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I agree.

My personal experience is that Lantus has a very small peak about 5-6 hours after a dose. I use it to my advantage by timing the peak to align with the times I most need it. Also, by doing 2 shots a day, you can time the gaps in basal coverage to the times of day you need less basal.

The NPH peak completely covered my lunch when I was a child. I can’t use Lantus to cover any meals.

Here’s a graph showing the general onset and peak of different insulins. Note: detemir = Levemir and glargine = Lantus