Bolus before or after certain meals

Until recently I had been using insulin up to 15 minutes before a meal. Some high numbers after more carbs led me to think I needed more insulin, but that had me going low.

Now I’m not entirely sure why, but the highs I get seem to come a couple hours after the meal. I was really not sure what to do, considering upping my daily Lantus has given me issues lately, and obvi upping Humalog had already not helped this situation. Then one day I was getting pizza for dinner, and had a bit of a realization.

I have known for a while now that greasy cheesy pizza, without fail, has given me highs later on after eating. But this time, thinking of my recent issues, I added another unit of insulin on to what I’d normally do for this same amount of food. ~5 minutes before eating it. 4 whole hours later, my number was above 300 for 30-40 minutes. I realized that the insulin is acting way too early when the carbs take that long to enter the bloodstream.

So could this issue with the pizza be similar to my usual post-meal problems? Or would that be wishful thinking, and I have some other things to consider. I can’t say the food I eat is anywhere near as fatty as this pizza I had - not even close really. What would I learn if bolusing after my later meals had me level out like I had been previously?

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I should also mention something I feel is never talked about with this 15 minutes before thing.
Sometimes injecting so early is pointless when you’re a slower eater. I guess I hadn’t considered that having an effect on me until now, but maybe that has something to do with it

The delayed spike is most likely your body converting over the protein and fat.
Your spike should be somewhat consistent at 2-3 hours, usually close to the 2 hour mark.
Based on that, you can give yourself a second bolus roughly based the protein and fat (It varies for everyone, but I count for 50% of protein and 10% of fat. So if you have 10g of protein, I would bolus for 5g of carbs.)


Conventional wisdom is that five grams for protein equals one gram of carbs in blood sugar impact and that unlike carbs, the delay can be more than two or three hours. Also that fat has no same day effect on blood sugar, though if you gain weight that will affect you. But the conventional wisdom is not always right, (one major point of this forum, yes?) so Hammer’s point is worth considering. Experience counts for a lot.


That’s a good insight. Matching the speed of the insulin to the speed of the food is an art that you’ll learn with practice. With MDI, for slower foods (and pizza is the famous example) the key technique is “split bolus” where part of the insulin is taken before the meal, and part is taken later (maybe 1 or 2 hours later.) And there’s no rule that says you can only take insulin twice for a meal. With a CGM I take insulin whenever I see on the graph that my BG is going up too far or too fast. — But I always have a tube of glucose tablets in my pocket, so I can recover if I overdo the insulin and need to catch a plummeting BG before it goes low.

Well the fundamental thing to keep in mind is what my CDE said: “If your blood glucose is too high, you need more insulin.” So for a meal where the BG goes up and doesn’t come back down, more insulin was needed. That’s not an issue of timing or split bolus, it’s just total insulin.

Prebolus has to do with giving the insulin a head start so that it can try to keep up with a fast carb. Split bolus has to do with slowing the insulin action down to match a slower-digesting meal. Changing the insulin:carb ratio has to do with matching the total amount of glucose that will be released by digestion so that the meal bolus doesn’t leave me at a sustained high or a sustained low after eating.

Bolusing to account for protein and fat in addition to carbs, like Hammer said, is sometimes called T.A.G. bolusing (for “total available glucose”.) It helps for people eating low-carb, or for meals that are really heavy in fat/protein, but for people like me who get half my calories from carb, the protein and fat content are small enough that I don’t figure them into the meal bolus, I only think about them in terms of slowing down the digestion when I’m deciding whether to do a split bolus.


The foods I’ve found I need to split bolus for are veggie burgers with fries, pastries, and long, slow meals like Christmas dinner and raclette. I set an alarm for one hour after I start eating and do a second injection (and sometimes third injection in the case of Christmas dinner and raclette). I keep fast-acting carbs (mid-meal pie/hypo treatment, anyone?) close to hand in case I miscalculate my units or timing.

I am a very slow eater and I’ve had some periods where I’ve had to post-bolus at dinner or else I’d go low mid-meal. During those periods, I set an alarm and bolus 30 minutes after I start eating. I don’t know if I eat faster, digest faster or if I’m just less sensitive to insulin now, but a short pre-bolus (5-10 minutes) works for me these days for lunch and dinner. Breakfast is a completely different story.

You need whatever you need. There’s no need to stick with a 15 minute pre-bolus if it’s not working for you.