Keto Headache: Causes and What to Try
Quick answer: A headache in your first week or two of keto is usually one of two things. Salt and water are leaving your body along with your stored carbohydrate, and your body is missing the sugar it was used to and running a little short on fuel. Salt and broth often help within hours. Drinking more and more plain water can make it worse, because each bathroom trip takes more electrolytes with it.
In this article
- Cause one: salt and water leaving with your glycogen
- Cause two: withdrawal and the energy gap
- Why more plain water can backfire
- Which one is yours?
- What to try, today
- When to call your doctor
- What the research says
- KetoDick's take
- Key takeaways
Cause one: salt and water leaving with your glycogen
Your body stores carbohydrate as glycogen, and glycogen is stored with water. KetoDick's rule of thumb is that for every gram of glycogen you drop, you drop about two grams of water (video 9Hk0jRb_9Es). That's why the first week's weight loss is mostly water.
Salt goes with it. On keto the salty starches and processed foods are gone, ketosis leaves you less able to hold on to salt, and more water passing through means more salt passing out (video -dHjt_Bpruk). He lists headaches alongside cramping, irritability and low energy as signs your electrolytes are short (video lbRPlGZ3Rvw).
Cause two: withdrawal and the energy gap
The other early headache comes from the switch itself. In his telling, people strip away their glucose before they're efficient in ketosis, and then they can't sleep, they're lethargic and they get headaches, because the body is simply short on energy (video DoSUgIr2rNo). Fat adaptation takes weeks, so this can linger longer than the salt kind.
On top of that, he sees much of the first-week misery as withdrawal from sugar and carbohydrates. He says outright that this is more his opinion than science (video 9r2Y74AnjUQ).
Why more plain water can backfire
"Drink more water" is the standard headache advice, and on keto it can turn against you. His warning: every time you go to the bathroom you pass some electrolytes. Tell someone to drink more water and take more electrolytes and you put them on a "hamster wheel" (from the video): drink, pee out the minerals, need more (video RGfWR5jQNDQ).
If you're going all the time, in large amounts, and it's clear, he says you may be passing so many electrolytes that you cause keto-flu symptoms yourself (video RGfWR5jQNDQ).
So what you do is aim for pale yellow urine, not clear. Dark yellow or amber means drink more. Clear all day means ease off. (If you take a medication that changes urine colour, this test won't work for you.)
Which one is yours?
| Clue | Points to | First thing to try |
|---|---|---|
| Headache plus cramps or irritability | Low electrolytes | Salt and a cup of broth |
| Peeing clear, constantly | Over-drinking, flushing minerals | Less plain water; add salt |
| Dark yellow urine | Not enough fluid | More water, with salt |
| Headache plus heavy tiredness, poor sleep, weeks 1–2 | Energy gap before adaptation | Eat to fullness; don't cut calories yet |
| Cravings, cranky, rotten mood | Carb withdrawal | Time; keep carbs steady |
Based on videos lbRPlGZ3Rvw, RGfWR5jQNDQ, DoSUgIr2rNo and 9r2Y74AnjUQ.
What to try, today
- Have a cup of salted broth or bouillon. His beginner routine is one cup twice a day (video UygKGoP_BtA). He says electrolytes work quickly: drink one in the morning and you should feel better before lunch (video -dHjt_Bpruk).
- Salt your food more than you think you need to. Most of the salt in your old diet was in foods you've dropped.
- Check urine colour and adjust water as above.
- Eat enough. In weeks one and two he says don't track calories, eat until you're full, and just avoid carbs (video DoSUgIr2rNo).
- Eat leafy greens for magnesium and calcium (video lbRPlGZ3Rvw).
When to call your doctor
Talk to your doctor before you add salt on purpose if you take blood-pressure medication or have been given a sodium warning. That's the group he says his higher sodium numbers don't apply to (video -dHjt_Bpruk). Do the same before any potassium or magnesium supplement, especially with kidney or heart history (video lbRPlGZ3Rvw).
A headache that is sudden and severe, or different from your usual, or that keeps getting worse instead of fading, isn't keto flu to wait out. Get it checked.
What the research says
- Timing: online reports of keto flu symptoms cluster in the first weeks and are mostly described as transient (Bostock et al., 2020). That study read posts; it didn't examine anyone.
- Salt loss: insulin, with blood sugar held constant, reduced sodium and potassium excretion in healthy men (DeFronzo et al., 1975), the usual explanation for why salt leaves faster when insulin falls on low carb. PubMed searches on 2026-10-30 found no highly cited trial directly measuring that on a ketogenic diet in adults.
- How much sodium: NASEM sets adult adequate intake at 1,500 mg/day and says to reduce intake if it's above 2,300 mg/day (NASEM, 2019). The American Heart Association's 1,500 mg "optimal goal" comes with a note that it may not apply to people losing large amounts of sodium in sweat (AHA).
- His number vs theirs: in 2018 he aimed for about 5,000 mg of sodium a day, citing a mortality study (video -dHjt_Bpruk). That is well above the NASEM and AHA figures. The broth post covers that study and the debate around it.
No study on the evidence pages tests headache treatments on keto. The steps above are his practical approach, built on the mechanisms.
KetoDick's take
He thinks "electrolytes" said vaguely is half the problem. Name them, sodium, potassium, magnesium and calcium, and it gets much easier to see where each one comes from (video lbRPlGZ3Rvw). And he'd rather you stopped calling a headache "keto flu" at all. It isn't flu, and in his opinion it mostly isn't keto; it's a fixable salt problem, a short withdrawal, or a body still learning to run on fat (video 9r2Y74AnjUQ).
Key takeaways
- Early keto headaches are usually salt-and-water loss or the energy gap, often both.
- Glycogen leaves with water, roughly two grams of water per gram by his rule of thumb, and salt goes too.
- Salted broth often helps within hours.
- Pale yellow urine is the target; clear all day means you may be flushing electrolytes.
- On blood-pressure medication or a sodium warning? Ask your doctor before adding salt.
- Sudden, severe or worsening headaches need a doctor, not a timeline.
Related
- Guide chapter: Electrolytes · Keto Flu · Hydration · Water Weight
- Blog: How Long Does Keto Flu Last? · Is Keto Flu Real? · Broth for Keto Flu · Leg Cramps on Keto · Urine Colour and Hydration · Why Do I Pee So Much?
- Videos: It's not keto flu · Making sense of electrolytes · Am I getting enough water?