Day Three on Keto: Why Ketone Strips Show Only a Trace, and Why the First Two Weeks Are Hard

2017-07-18

This is a 90-second reply I recorded on 2017-07-18 for someone on their third day of keto whose strip had only just started to change. It came about two weeks before my first YouTube upload, and it's never been on YouTube. It's short, but it holds the whole month-one pep talk in one breath (live ISEE4654).

In this recording

[0:00] Why you probably only see a small trace on day three: your muscles and liver still hold stored carbohydrate (glycogen). I gave 700 grams as the figure for an average adult man, less for women. At about four calories a gram, that works out to 2,800 calories, or about a day and a half of fuel. So even someone fasting completely would only just be reaching ketosis around day three.
[0:42] Stay strong. Day three is terrible, and days four, five and six might be worse. It got better after that for me. The first two weeks are generally hard, so don't expect to lose much besides water weight.
[0:42] Then, around weeks three and four, appetite "starts melting away" (machine transcript). You stop feeling like you need to eat, and a calorie deficit happens on its own, without restriction.
[1:23] For the first two weeks, don't worry about results. Just make it through.

Watching this in 2026

What I like here is the order. First the mechanism (why the strip is faint), then the expectation (it gets worse before it gets better), then the one instruction (just make it). There's no supplement list and no macro chart. Somebody on day three doesn't need a lecture. They need to hear that a faint strip is normal and that week three is coming.

One thing I'd add now: the 700-gram glycogen figure was my number, and none of the evidence pages for this site check it. Treat it as a rough picture, not a measurement. The idea behind it is on solid ground, though. The liver makes ketone bodies (acetoacetate, BHB and acetone) under the control of insulin and glucagon (StatPearls, Ketogenesis). Cahill's review of starvation describes the body moving from glucose to fatty acids and liver-made ketones as stored carbohydrate runs down (Cahill 2006). So there really is a lag before ketones climb, and day three is early.

Drill-down: is "the first two weeks are terrible" fair?

I called it "survivor mode" (machine transcript). That's a strong phrase, and I stand by the reason for it: if you warn people, a bad week doesn't feel like failure.

What the literature shows is narrower than "terrible." One study read people's own online posts about keto flu. It found the symptoms clustered in the first weeks and were mostly described as passing (Bostock 2020). That's self-report, not a trial, but it matches the shape I described: early, rough, temporary. Later I'd argue that much of what people call keto flu is carb withdrawal plus low electrolytes. That's in Is keto flu real? and the keto flu chapter.

One caution I didn't give in 90 seconds. If you take medication for diabetes or blood pressure, cutting carbs can change what dose you need, sometimes within days. Talk to your doctor before you start, not on day three. See keto with diabetes or blood-pressure medication.

Then vs now

Two weeks later I recorded a week-by-week timeline: water weight in week one, a slog and a plateau in weeks two and three, real fat loss from about week four (video uDw65ERtsA0). Two years later, kicking off a group reboot, I told people almost the same thing: a quick drop in week one, often nothing in weeks two and three, sometimes four, then it gets easier (live JDDW2290). The story stayed the same. The "survive it" tone got gentler.

I also said here that the strip reacting at all is the signal. A few weeks later I explained why strip darkness stops tracking anything once you adapt (video 8wOheKcBEd8). So a faint strip on day three and a fading strip in month two are both normal, for different reasons.

Key points

On day three, stored glycogen is still being used up, so a faint strip is expected (live ISEE4654).
The 700 g / 2,800-calorie figure is my 2017 estimate. This site's evidence pages don't check it.
Days three to six are often the worst. Expect mostly water-weight loss in the first two weeks.
Appetite usually drops around weeks three and four, and that's when the easy deficit shows up.
On diabetes or blood-pressure medication? Talk to your doctor before you start.