Track Low Blood Sugar and What Comes Before Each Hypo

Low blood sugar, or a hypo, is when the glucose in your blood falls too low for your brain and body to work normally. For people treated for diabetes, the NHS and the American Diabetes Association draw the line at 4 mmol/L (70 mg/dL). It usually announces itself with shakiness, sweating, sudden hunger, a pounding heart, tingling lips or irritability, and if it keeps falling, with confusion, blurred vision, slurred speech and clumsiness. Most hypos happen in people taking insulin or sulfonylureas, but some people without diabetes have reactive drops a few hours after eating. A meter tells you the number at one moment. A diary of each episode, how it felt, how bad it got and what came before it, shows the pattern behind the numbers.

Why track this symptom?

  • Hypos that repeat at the same time of day or after the same activity point to a dose, meal or exercise pattern your care team can adjust.
  • Grading each hypo by what it did to you, not only by the reading, is how clinicians judge hypo risk.
  • A run of hypos you noticed late, or only when someone else did, can be an early sign of fading hypo awareness.

How Trace Health helps

Log a hypo in one tap once you have treated it: mild if you felt shaky, sweaty or hungry and sorted it yourself, moderate if you were confused, weak or struggling to think or act, severe if you needed someone else's help or glucagon, or passed out. Mark it Gone when you have recovered, so each episode has a start and an end, and add a note with what you treated it with and what you were doing. Log high-carb meals, skipped meals, walks, alcohol, stress, sleep, medication and injections on the same timeline, and Insights show which of them line up with your hypos. Trace Health does not read or store glucose values: your meter or CGM keeps the numbers, Trace keeps how you felt and what happened.

Common causes

In diabetes, a hypo is a mismatch between glucose-lowering medication and the glucose available. Insulin, and tablets that make the pancreas release insulin, such as sulfonylureas (gliclazide, glimepiride, glipizide) and meglitinides, cause most of them. The usual triggers are a meal that was delayed, skipped or smaller than the dose expected, more physical activity than usual (its glucose-lowering effect can last up to 24 hours, so lows often come overnight), alcohol, which slows the liver's release of glucose for hours, especially when drunk without food, a dose taken twice or at the wrong time, and injecting into a warm or recently exercised area, which speeds absorption. Weight loss, kidney disease and recovery from an illness can make a familiar dose too strong. Metformin, DPP-4 inhibitors, SGLT2 inhibitors and GLP-1 medicines rarely cause hypos alone, but can when combined with insulin or a sulfonylurea. Without diabetes, reactive hypoglycemia can follow a meal within about four hours, more often after stomach or bariatric surgery or in prediabetes. Hypos while fasting in someone without diabetes are uncommon and can reflect alcohol, some medicines, liver, kidney or hormone problems, or rarely an insulin-producing tumor.

When to see a doctor

Call emergency services if someone is unconscious, having a seizure, or too drowsy or confused to swallow safely. Do not put food or drink in their mouth; turn them onto their side and give glucagon if it has been prescribed and you have been shown how. If you are treating your own hypo, clinicians commonly advise about 15 to 20 grams of fast-acting carbohydrate, such as glucose tablets or a small glass of juice, a recheck after 15 minutes, a repeat if you are still low, then a longer-acting snack if your next meal is not due. Follow your own care team's plan. Contact your diabetes team soon after any severe hypo, if hypos become more frequent, if they happen at night, if you notice them later than you used to or not at all, or after a medication change. If you have hypo-like episodes and do not take glucose-lowering medication, see a doctor for an assessment rather than treating them as normal.

Frequently Asked Questions

How do I know if what I feel is low blood sugar?

The early signs come from the adrenaline your body releases to push glucose back up: shaking, sweating, a racing heart, sudden hunger, anxiety, tingling lips and paleness. As the brain runs short of fuel, a second wave follows: difficulty concentrating, confusion, blurred vision, slurred speech, unusual behavior, irritability and weakness. Many of these overlap with anxiety, panic or simply being hungry, which is why a reading matters: if you have a meter or CGM, check when you safely can, but never delay treatment to do it. Over time, a log of what your own hypos feel like shows your personal early warning signs, which are often more specific than any list.

What do mild, moderate and severe mean for a hypo in Trace?

Trace grades a hypo by what it did to you, the way clinicians do, rather than by a number. Mild means you felt shaky, sweaty or hungry and treated it yourself. Moderate means you were confused, weak, or found it hard to think or act. Severe means you needed someone else's help or glucagon, or passed out, which matches what the American Diabetes Association calls a level 3 hypo, whatever the reading. Mark the entry Gone when you have recovered, so the length of the episode is recorded too. Severe hypos are the ones every diabetes team wants to hear about, and the grading makes them easy to find in your history and in the report.

Why do I have hypos at night, and how can I tell?

Night hypos are common in people using insulin or sulfonylureas, particularly after evening exercise, alcohol, a light or early dinner, or a long-acting insulin dose that has become slightly too strong. They are easily missed. Clues include nightmares or restless sleep, waking with damp sheets or night clothes, a morning headache, and feeling unusually tired, hungover or low on waking. If you use a CGM, its overnight trace is the best evidence. Log Night Sweats or a Low Blood Sugar entry when you find the clues, and log what you did the evening before, then show the pattern to your diabetes team, who may adjust the timing or the dose.

Can I get low blood sugar without diabetes?

Yes, though it is less common and deserves a doctor's assessment. Reactive (postprandial) hypoglycemia causes shakiness, sweating and hunger, usually within four hours of eating and often after a meal heavy in refined carbohydrate. It is more common after stomach or bariatric surgery and can appear in prediabetes. Lows while fasting, or episodes with confusion or fainting, need prompt investigation, because causes include alcohol, some medicines, liver, kidney or hormone conditions and, rarely, a tumor that makes insulin. Doctors usually look for a low reading captured during symptoms, with relief once you eat. Logging each episode and what you ate beforehand gives them the timing to plan tests.

What is hypo unawareness, and can a log help spot it?

After many years of diabetes, or after frequent hypos, the adrenaline warning can weaken, so glucose falls further before you notice, or you only notice once you are confused. This is called impaired hypo awareness. It raises the risk of severe hypos, diabetes teams check for it, and in the UK it affects driving rules. In a log it shows as fewer mild entries and more moderate or severe ones, or as hypos that someone else spotted before you did. Diabetes UK notes that carefully avoiding hypos for a few weeks, with your team's help, can bring some warning signs back. Trace Health keeps the felt side of each episode, which your meter cannot.

Your health data stays on your iPhone.

No account. Private. No personal information is ever requested. Your health data stays on your iPhone by default. A backup option to your private iCloud is available. Trace Health never collects or sells your health data.

What people say

Rated 4.8 out of 5 from 66+ ratings on the App Store.

  • “Out of all the symptom tracker apps, I found this to be the easiest and most straightforward. It “writes” to the health app, which is exactly what I wanted. All the others only “read” parts of the health app data, and didn’t truly write any data back. This helps me visualize my chronic symptoms soooo well.” (EB1700, United States)
  • “I’m not really into tracking mood and habits but this app has shown me the benefit of doing so and has helped me reflect on my day to help find the positives and see where I can improve.” (GavinLanoe, United Kingdom)

Read the complete guide: How to Keep a Hypo Diary Your Diabetes Team Can Use →