New Dexcom

I got my Dexcom right before I left for a summer vacation. It "saved" me twice by alerting me to dropping BG levels.
Now that I am back home I am having a difficult time determining when my Humalog will respond. I have had some days when I am right in range and other days when I eat breakfast and peak 3-4 later and stay high until evening.
I also drop at about 3:30 AM after taking a 9 PM Lantus dose.
Does anyone have any references which will help me to understand whta is going on?

Hi, congrats on the Dexcom, it will help you figure things out.

I don't know how much experience you have with diabetes 101 but humalog kicks in about an hour after injection and can continue to drop your bg for 4 hours. On the other side, different foods will impact your bg at different times. A meal higher in fat/protein will can cause a peak 3-4 hours later. What I do is eat the same meal and fingerstick at regular intervals until I figure out how much and when to bolus for that meal. This all assumes your Lantus dose is correct and is holding you more or less steady. Lantus always had a peak for me around the 5-6 hour mark after injection. I would typically drop 30 points and often more. Hope this helps.

Thank you for your comments.
So my Lantus is peaking just at the time that you are indicating shot at 9PM is causing a drop six and one half hours ;ate (3:30 AM).