I have been diabetic for about ten years now but looking around this site I think I missed a few lessons.
What is the procedure for pre-bolusing and when is it appropriate?
Can you treat a low with a pump suspend? If so how?
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We find a pre-bolus is helpful to match the action of the quick food with the slow insulin. If you have a cgm it makes it easier to see the play by play action of the impact of the food and insulin.
@Pixari - Do you have a cgm?
IMHO, the answer to both your questions are a bit different if you have a cgm. Doesn’t mean you can or can’t do either but I think the approach may be different.
Pre-bolus is a technique you use for dealing with most meals (unless they are small snacks of low GI), and which, when used well, can avoid most post-meal spikes. We use it at every meal - would never even consider not doing it. Here is a wiki on it:
Beware the fact that it requires a good bit of personal experimentation to figure out exactly (a) how long you need to pre-bolus by, and (b) how to adjust it to meal size and GI, and, in some cases, time of day.
As for us, we always do better pre-bolusing, but we don’t always get it just right.
I’ll let pump experts deal with lows and pump suspends. We are new to pumps so still naive – but, since it takes quite a while (for us, 1-2 hours) for the body to react to basal changes, we would not, at this stage, treat a low with only a pump suspend, unless we can see it coming from very far away 
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Sure you can treat a low with a basal reduction, but it works much better if you use a CGM and lower your basal when you are at 100 and dropping. Then your basal reduction has time to reduce the drop. If you combine that with a few carbs (4 or so for us) then you can prevent a low, and turn a downward trend into a sideways trend.
Agreed. Some times, a foreseen low is the case. Certainly not always. If the CGM shows a nose dive and it is already on 90 and dropping super fast then clearly fast carbs are needed. And if there is substantial IOB then potentially even more carbs.
But as @WestOfPecos says, if you can see the low coming and have time (as mentioned in the 1~2 hr range) then certainly a temp basal (whether suspend or partial reduction) can be quite effective and potentially bypass the need for carbs to correct what WOULD HAVE BEEN a low.
Pump manufactures are spending time and money to build this into their products.
The next big update from Tandem is going to be Predictive Low Glucose Suspend (PLGS):
“Tandem Diabetes [clip], today presented results from a feasibility study for its predictive low glucose suspend (PLGS) algorithm, designed to suspend insulin delivery when low blood sugar is predicted.”
June 12, 2017
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I have an old Medtronic at the moment
@Pixari - Is that only the pump or do you also use one of the Medtronic cgms?
Or do you have the newest 670g fully integrated model? (In which case the answer would be totally different - I think.)
I have the CGM but the system is older
In which case, I believe all the above information is completely spot on for you.
Thank you everyone 
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You’ve been given a lot of good advice already.
Like a lot of things about diabetes, it depends. I’ve been wearing a closed loop artificial pancreas system since last November and temporary basal rates, including a zero temp basal rate, are how the system attempts to steer blood glucose levels.
When I first heard this notion, I thought it impractical since insulin takes 90-120 to peak and it could not produce any near term effect in BG levels. I was wrong. I am amazed at how much temp basal rates can help with a trend if you’re watching closely enough.
In me, I find basal rates changes effecting BG levels in the 15-20 minute range if my blood glucose is drifting and there are no large boluses of insulin or food trying push my CGM line forcefully up or down.
But I would not use the pump suspend function because that means you’ll have to return at a later time to unsuspend it. And sometimes you might forget, check that, you will forget and then have to deal with correcting a high. I would set a 30-minute temp basal to zero and test for the effect you want. After 30 minutes, it’ll just time-out and revert back to your regular basal program.
Experiment and track your results. You can get better with time.
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I would decrease the temp basal, but not suspend. So, I agree with Terry and the others.
The concept of adjusting temp basal rates is both foreign and intriguing to me. I don’t currently pump, but it’s often been one of the things that has drawn me to wanting to get a pump.
I feel my control is already pretty tight, but I wonder what kind of advantages I could get from that.
I find it wiser to use a temporary basal rate of zero, than to Suspend, because too often I’ve forgotten to turn off the Suspend until many hours later, so don’t make the same mistakes that I have. Sometimes I get lazy and hit Suspend, because it takes fewer button pushes on a MM pump to do that, than to set the basal rate to zero percent for x number of hours.
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On my Minimed pump the temp basal also won’t beep at me With suspend it somewhat annoyingly beeps every five minutes…
That does sound safer. I will try that, thank you.
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Kenrick, I can’t hear the SUSPEND beep very often because I’m either out and about being very active, where there’s no way to hear the wimpy beep, and if my pump is under bedcovers, no way can I hear it. MM pump beeps are woefully inadequate. I’m so glad that the G5 receiver has loud alarms that should wake me (haven’t had a low yet, while asleep, but only had the G5 for 4 days) up, since I can leave it on the nightstand instead of having it clipped to my shorts, like where my pump is located–that puts the pump under the covers, and therefore makes the alarms all that more unnoticeable.
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The theory behind prebolusing goes like this, allowing for a bit of poetic license or oversimplification:
Your own endogenous insulin (if you have any) is released whenever your blood sugar starts to climb sharply, and begins working almost immediately. So in a nondiabetic person, the net result is that the two things occur very close together in time so that blood sugar never climbs very high.
That scenario is what we are trying to mimic as closely as we can. So if the insulin you are taking starts to work half an hour after you take it, the idea is to take it half an hour before you sit down to eat. That way the insulin and the food begin working at the same time. That’s as close as we can get to replicating what a healthy pancreas does.
Obviously this approach needs to take into account your particular circumstances, e.g., the type of insulin you use, how long it takes to start working, what kind of food you’re eating, etc. So the timing needs to be determined by you based on your knowledge of how your body works and what’s happening.
But that’s the basic idea.
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I think the pre-bolusing tactic is one of the most overlooked yet highly effective insulin dosing tactics. I only used it occasionally in my early years with diabetes.
One of the things that held me back was when I used Regular for my meal insulin. Unlike the current rapid acting analog insulins, Regular had an onset time of 30-60 minutes, a peak action of 2-4 hours and a duration of 6-8 hours. Talk about an unruly tool to use! I once fell asleep after I took my meal pre-bolus of Regular insulin. When I woke up on the floor, I thought aliens had invaded my apartment!
So, this is still the main safety hazard with pre-bolusing. You just can’t lose sight of the fact that you took your dose! As we know, the phone can ring or someone can knock on your door and distract you from your intention to eat. I think setting a phone alarm is a good safety practice. The rapid acting analog insulins make pre-bolusing safer than it was with Regular.
Using a CGM to discern when your meal insulin dose starts to bend your CGM line down is a good way to learn what your ideal pre-bolus times are. For me, I need to pre-bolus a longer time for my morning meal than I do for my evening meal. My morning pre-bolus time is usually 60 minutes but sometimes I need to shorten this time and my CGM helps with this dynamic shift. My evening meal does well with a 30 minute pre-bolus time.
For those who use multiple daily injections, or MDI, just do a few fingersticks at dose-time followed by fingersticks every 10 minutes. You won’t need to do this for every meal into the future; you will learn a few safe rules-of-thumb that work for you. If you keep a record of this you should be able to make the pre-bolus tactic work for your own unique needs.
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I have the Animas Vibe - ‘Suspend’ also turns off the CGM, so I use it only for times when I want to upload data from my pump (mandatory then). The CDE who was supposed to train me (I opted out of the training, as it was my 3rd pump in a year!) only gave me one big piece of advice: us a temp basal instead of suspend whenever possible
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