No matter how you celebrate the winter holidays, I’ll bet that you do it with rich and sweet comfort foods. You probably splurge more than usual — in every way, but with food especially. You probably exercise less. You might, generally speaking, adopt a temporary philosophy of indulgence. You might be a bit less fussy about your insulin management.

Diabetes demands that you constantly balance short-term pleasures against long-term consequences. It’s certainly something I think about dozens of times a day. Around Christmas and New Year’s, it feels natural tilt that balance towards short-term pleasure.

We would never tell you to completely stifle these indulgent impulses — people with diabetes should be able to enjoy good holiday cheer, and easing up on the intensive diabetes management can feel pretty great … when it doesn’t lead to hypos and blood sugar rollercoasters, that is. There’s no denying that the holidays can be problematic for glucose management, and it’s good to keep the potential issues and consequences in mind.

Holidays and High Blood Sugar

With so many people wearing continuous glucose monitors (CGMs) these days, some of the best data on blood sugars now comes from start-ups and tech companies. Glooko, a mobile diabetes health platform, releases a treasure trove of data almost every year.

In its 2020 report (PDF), Glooko revealed that all of the highest blood glucose days of the year occurred on major holidays. Glooko customers had their highest average blood sugar readings on:

  • New Year’s Day (185.5 mg/dL)
  • Christmas (182.6)
  • Valentine’s Day (179.5)
  • Thanksgiving (178.6)

And this was during 2020, the first year of the pandemic, when many Americans had holiday celebrations that were more mellow and small than usual.

Glooko users check their blood sugar most often during the weekday, and least often on the weekend. Their blood sugar reliably spikes up on Saturday and Sunday, and then goes back down until Thursday, at which point it goes back up again. The difference is not huge — a low of 178 mg/dL on Thursday, and a high of 184 mg/dL on Sunday — but the cycle might be familiar to anyone with diabetes.

Winter and Higher A1C Levels

Several academic studies have also attempted to measure the degree to which glucose control slips over the holidays.

A 2014 study in Diabetes Care looked at 3,212 English adults with diabetes (both types) over a period of years, and found that both A1C and cholesterol peaked in the 31 days after Christmas.

Here’s a graph from the article that puts it into perspective:

Jones A et al. Diabetes Care

This data suggests that English patients controlled their diabetes best during the summer and early autumn (a result that agrees with Glooko’s numbers). The average A1C increased nearly 0.5 percentage points from September to January, and average blood sugar climbed 0.8 mmol/L (about 14 mg/dL).

Does it matter? Well, maybe not. The researchers called these changes “small” and “transient,” and warned that medical providers shouldn’t read too much into those holiday numbers, because they’re likely to improve quickly. The change was indeed short-lived, as you can see that blood sugar levels immediately declined in February, perhaps a result of healthy decisions during New Year’s resolution season.

Little Changes Can Add Up

An older study from China, however, suggests that winter excesses can contribute to lasting blood sugar problems. Christmas is not a major holiday in China, but the world’s most populous country has its own winter celebrations around the same time, and the researchers explain that people over there enjoy the season rather like we do in the West: “During the winter holidays, people are customarily physically inactive and they enjoy salty meals and alcoholic beverages.”

This study looked exclusively at patients with type 2 diabetes, a condition that sadly usually gets worse year by year, with A1C slowly rising (often despite the use of stronger drugs). Looking at seasonal A1C data, the study concluded that winter holidays play a big role in the significant increases in A1C that patients with type 2 tend to experience as they age. In this case, while blood sugar did tend to improve in February, it usually wasn’t enough to counter the big spike during the holiday season; some percentage of the holiday blood sugar increase was therefore permanent.

The authors warned that small permanent increases — the paper found a 0.2% rise in A1C from November to March, a rise that “might not appear to be clinically important and could easily go unnoticed by both subjects and physicians” — can add up to huge problems if they occur year after year.


Although we know that most people experience higher blood sugar levels in the winter, we don’t know how often it’s a significant problem. Some people can strategically tolerate higher glucose values during the holidays, and get back into their healthy habits and normal level of control soon after. Others, however, may let bad holiday habits creep into their lifestyle.

We wish you a merry, happy, and joyful winter holiday. We hope you enjoy yourself — but please don’t completely lose sight of your long-term health goals. A little short-term hyperglycemia isn’t the end of the world, but it’s worth considering how you can make sure that holiday blood sugar issues don’t follow you into the new year.

Glooko Diabetes Data Annual Report. Glooko (PDF).

Jones A et al. Effect of the Holiday Season in Patients With Diabetes: Glycemia and Lipids Increase Postholiday, but the Effect Is Small and Transient. Diabetes Care. April 10, 2014.

Chen H et al. A Prospective Study of Glycemic Control During Holiday Time in Type 2 Diabetic Patients. Diabetes Care. February 1, 2004.

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Read more about A1c, beta cells, Christmas, diabetes burnout, exercise, Glooko and Diasend, holidays, insulin, Intensive management, low blood sugar (hypoglycemia).

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