Basal or Bolus?

I've been Type 1 for 21+ years and am on MDI. My insulin to carb ratio is a very simple l:10 (Apidra); correction factor an easy 100; and my Levemir basal 3 units in the morning and 5 at bedtime. So what could possibly go wrong? Today I accidentally took 5 units of Levemir in the morning instead of 3. I reduced my bolus by one third for the rest of the day and never went low with a Levemir peak, so there really wasn't a problem. I was surprised at how easy the adjustment was, although I think that 3 is safer. Assuming that lows wouldn't become a problem, which strategy seems better, 3 units of basal in the morning and using the 1:10 ratio for bolusing, or going with more basal and smaller boluses? Or maybe it doesn't really make a difference...

This is an interesting question and I'm going to start with the "stock answer". Your basal should hold your fasting blood glucose steady with no more than a 30 point rise or fall. If your basal is too high and you offset the extra insulin by taking less bolus at meals, you run the risk of going low if you miss a meal for some reason.

On the other hand, when I'm having trouble with highs I will sometimes just increase my basal by 20% or so to hold things down and then eat little snacks as necessary. I find using basal to cover some of my carbs this way a relatively easy and safe way to handle moderately high numbers during the day. However, I don't think of using basal this way as a long term solution.

It's one thing or another but it's always insulin.


IMHO you’re better off taking more basal and less bolus if possible-- less volatility. Basal doses if they’re anywhere near where they should be aren’t likely to cause your BG levels to plummet dangerously whereas bolus doses if off just a tiny bit (and they often involve educated guessing) can cause problems very quickly.

I think there's some overlap with bolus and basal. I snack a lot because, well, I like snacks but, if I bolus for 10G of carbs and eat 7G of carbs worth of pistachios, it will still end up pretty smooth, maybe trend down a bit and I have a beer when I get home or some more carbs before I run. I agree that you want your BG to be pretty flat on basal alone.

Hi Trudy,

I guess it depends on how you were doing before. If you were ok before I would go back to that. My basal has never kept me stable ever. I did what you did once- took basal for a bolus and it seemed to make no difference that day so I guess it was one of the days I was running higher for whatever reason. I didn't change anything, no extra food as I recall but that was quite a while ago.

I'm a math guy... so just for the heck of it lets take a look at your example through a mathematical lens.

Your correction factor is 100. Most of us consider bolus to be active for 3 hours, so lets say 100/3 = 33 points per hour over the course of 3 hours..

We generally assume levemir lasts 12 hours... and your normal dose is 3 units... so your levemir dose is essentially 3/12 = .25 units per hour. since we just established that 1u bolus reduces you 33 points in an hour, the same rate should apply to basal (after all insulin is insulin, only the delivery and absorption methods are different) So .25x 33 = about 8. Your normal dose of bolus counteracts about 8 units of BG rise per hour.

You accidentally increased your basal to 5. 5/12 = .417. .417 units per hour for the duration of your basal. .417 x 33 = about 14. So your increased dose, in the theoretically perfect math world would have countered 14 points of bg rise per hour.

14 -8 = 6. So, theoretically, it should have only made a 6 point difference in your bg over its duration.

I realize as much as anyone that we don't live in the perfect mathematical world, but penciling things out like this help me, and would also have made me think that you'd see little difference from that much basal increase...

If you think about it you took an extra 2 units which over 24 hours is only 1/12 unit extra per hour. Given your ICR, you wouldn't need even a single gram of carbs an hour to compensate for the extra insulin. I'm not surprised it didn't cause any trouble.

A typical basal/bolus split should be 50/50 on a high carb (45-60 g per meal) diet. As others have suggested you seem to be taking a much lower amount of basal than would be expected. Everybody is different, but the real question is whether your basal is actually set properly to maintain your blood sugars when fasting. If you skip meals during the day and go more than 5 hours since eating, does your blood sugar rise? Do you have a rise overnight?

I personally don't think it is a good idea to use your basal to cover meals or to employ your mealtime bolus to make up for basal deficiencies. In both cases this will cause your blood sugars to run higher or lower than they should for optimal control.

Thanks, Everybody. I was looking for information, and you gave me a lot. As a writing major, rather than a math major, I do appreciate all your calculations! (I eat from 100 to 130 carbs daily.) I've been a little concerned about whether or not I'm taking enough basal ever since I hit 537 BG a while back and was told by TuD commenters that I didn't go DKA because of the basal on board. On the other hand, I got the first dangerous low I've had in months while sleeping just this week. Last night at 3:00AM I was 94 and woke up to 200 this morning. I'm confused! I took 4 units of Levemir this morning, instead of my usual 3, and think I'll try that out for a while. Thanks again, I appreciate all your comments very, very much.

I think keeping the basal and bolus needs separate make day to day analysis easier. I know, in the real world, we cannot perfectly dose for each so it's inevitable that basal insulin sometimes cover bolus needs and vice versa.

You made a rational adjustment and it worked. Good move! I would not adopt this one-time fix as permanent because I think it can cloud future dosing decisions.

I've employed a variation of what you did using my pump basal to counteract a meal insulin overdose. This can happen, for instance, when I'm more active than usual and don't scale back my meal dose and then discover soon after I eat that I'm going low. In addition to taking a glucose tab or two, I may reduce my pump basal rate for an hour or two, sometimes reducing the basal rate to 0.0 units per hour. Basal adjustments, by their very nature, take hours to play out, so it can be a risky tactic and usually needs close attention. The last thing anyone wants is an unexpected ride on the gluco-coaster!

You're pumping, right Marty?

Sam, no need for all the caveats -- while we don't live in a "perfect math world", we do live in a math world when it comes to dosing insulin. While it's not a perfectly accurate methodology, what you ran through above is very pertinent -- after all, when we figure doses we're making the same calculations (albeit more simplified) to figure dosing.

Nice work!

Trudy, surely you're not saying that 94 is a dangerous low. It's not dangerous by any means, and is in fact a bit above average "normal".

While your own personal goals may include staying above that level in an abundance of caution -- which is fine -- please understand that unless there is something particularly different about your glucose metabolism, 94 is nothing to be concerned about.

Generally, I try to follow a pretty simple rule: Any BG control related to eating plus 3 hours is a bolus issue. Outside that, it's managed through basal.

This is only really possible with a pump, where you can set up variable basal programs. As a consequence, my normal day-to-day basal program varies through the day, increasing in the early morning through 9am to counter Dawn Phenom, and then again around dinner (5-8pm) to counter some other phenomena when my BG tends to rise 20-30 pts or so. I have other specialized programs for illness, etc.

Point is, actual basal needs, and insulin sensitivity, are not fixed -- they vary through the day.

No, no, no, Dave! Two different nights. The night I went low, I was basically unconscious and flailing around. My husband got a couple of DanActives (a yogurt drink, 14g carbs ea.) in me as I came around. Last night I thought my 94 was great, and I don't understand why it went up to 200 at 8:00AM. I'm hoping things will settle down, as I make sure to keep the number of carbs low at dinnertime.

Basal adjustments, by their very nature, take hours to play out, so it can be a risky tactic and usually needs close attention.
As they say in da 'hood, "werd".

This hours-long delay in subcutaneous administration has got me really interested in experimenting with intramuscular injections for corrections, which I'm planning to try out this weekend.

I'm going to have measured amount of carbs without bolusing, wait 60-90 minutes for BG to peak, then try an IM correction and see how it responds. Should be interesting.

Logical and well presented. Just a couple teeny tiny caveats. Basal insulin, as mentioned earlier, is meant to keep BG stable when NOT eating. Another way to say that is, it's meant to counteract liver dumps (actually steady liver "trickles" in this context).

So, calculating basal insulin using ratios established for bolusing might -- or might not -- match up with the rate at which carbs are entering your blood from the liver. In other words, if 1 unit of bolus insulin covers 10 carbs, applying that to basal computations assumes that you know when exactly 10 carbs are being released by the liver. Unless you've done some controlled testing to determine that, you could be off by a lot or a little.

. . . not to mention the fact that it'll probably vary by time of day, physical activity, phase of the moon and whether Aquarius is in trine with Neptune, etc.

And, just to complicate matters further, we are told that 1 unit of insulin has the same effect no matter what type of insulin it is. Actually, that turns out not to be the case. Different insulins have different effects, something the manufacturers do NOT tell you. For instance, 1 unit of regular covers 8 carbs in the morning hours for me. 1 unit of Apidra covers 12. That's by actual measurement, not guesswork. And it's not the least bit uncommon.

The bottom line is what it always is with this insane disease: empirical measurement is the only way to get safe, reliable, true answers.

I have used IM corrections for years when I need a faster response. Works like a charm, but . . . . that's me. "Your results may vary."

Also, if you're going to experiment with IMs, which in my book is a good idea, try different sites. Many people find that the speed of action varies considerably. For me, the deltoids are the fastest and most consistent. You'll need to determine what works best for you.

I’ve had success working out the muscles near the sub-cu shots,running,walking, running stairs and push-ups. IV shots too but I only do that if I get crazy high, like 250+ and I hardly ever do that these days.

A hot shower seems to drastically increase the absorption rates of subcu bolus for me… To the point that I make sure not to shower with bolus on board unless I’m trying to make the bg drop fast

There have been times when I could have really benefited from an IV, but I'm just too paranoid about bubbles.