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You check your watch in the morning and your resting heart rate is up. Maybe it's usually 62 and now it's sitting at 70 or 72, a week or two into carnivore. That's unsettling when you started this to get healthier.
Here's the short answer. In the first few weeks, many people see a modest rise in resting heart rate because the body sheds water and sodium fast, which lowers blood volume, and the heart beats a little faster to keep blood pressure steady. Add some adaptation stress and a few rough nights of sleep, and the number creeps up. For most people it settles as they adapt, usually by weeks 4-6. A number that keeps climbing, or comes with other symptoms, is a different story, and I'll be specific about that below.
One note before we start. This post is about a steady, higher resting number. If what you're feeling is skipped beats, flutters or a pounding that comes and goes, that's a different topic, and I've covered it in our guide to heart palpitations on carnivore.
Why the number goes up in the first weeks
You lose water quickly. Your body stores carbohydrate as glycogen, and glycogen holds water. When carbs drop out, that store empties and the water goes with it. That's why week one often brings a 3-7 lb drop on the scale, a bit less for smaller or older bodies.
You lose sodium with it. Lower insulin tells your kidneys to let go of more sodium. Sodium is what holds fluid in your bloodstream. Less sodium means less blood volume, and less volume means each beat moves a little less blood. Your heart makes up the difference by beating more often. That's a normal, sensible response, not damage.
Your body is under some adaptation stress. Switching fuel sources is work. Stress hormones can run a bit higher in the early weeks, and they nudge heart rate up too.
Your sleep may be off. Sleep disruption is common in weeks 2-3. Most watches calculate resting heart rate from overnight data, so a restless night shows up as a higher number the next morning.
Is it water or salt?
Some people suspect they just aren't drinking enough to keep up with the fluid loss. Fair thought, but water alone often isn't the fix. If you drink a lot of plain water without replacing sodium, you can dilute what little sodium you have and feel worse.
Others find the "carnivore flu" feeling is really low electrolytes, and that they'd only been doing the bare minimum with salt. Here's what I've seen work for most healthy adults:
- Sodium: 3-5 g of sodium a day, spread across the day. One teaspoon of salt is about 2.3 g of sodium, so that's roughly 1.5 to 2 teaspoons of salt from all sources.
- Magnesium: 300-400 mg of magnesium glycinate in the evening, which can also help sleep.
- Potassium: food first. Meat covers most of it. We don't recommend potassium pills in any real amount, because too much potassium is dangerous.
- Water: drink to thirst. More isn't automatically better.
If you want the full breakdown, our electrolyte protocol for sodium and magnesium walks through timing and sources.
Important: if you take blood pressure medication, a diuretic ("water pill") or any heart medication, or you have kidney disease or heart failure, please don't follow those amounts on your own. Ask your doctor before adding salt, potassium or magnesium. Those medications change how your body handles all three, and your doctor needs to set your numbers. Some heart medications also hold your heart rate down, so your watch may not tell the same story it would for someone else.
How long does it usually last?
For most people, the rise is a few beats per minute and it fades as they adapt. The roughest days tend to be days 3-10, and most people feel settled somewhere around weeks 4-6.
It can happen again on a second attempt, too, so don't read it as a sign you're doing it wrong. Many people also find their resting heart rate ends up lower than where they started once they're adapted and some weight has come off. Your situation might be different.
The trick is to look at the trend, not a single morning. A seven-day average tells you far more than one bad night. For the bigger picture of what's normal early on, see our honest guide to the first 30 days.
When to call your doctor instead of waiting
A small bump that levels off is adaptation. A number that keeps rising is information, and it deserves a real look.
Some people find that what first looked like a diet adjustment turned out to be something unrelated, like iron-deficiency anemia or an overactive thyroid, that just happened to show up at the same time. Carnivore didn't cause those. But a new diet makes it easy to blame everything on adaptation and wait too long.
Call your doctor if:
- Your resting heart rate keeps climbing past week 4-6 instead of leveling off.
- Your resting number is regularly above 100 beats per minute.
- Your heart rate jumps very high with light activity, like walking to the mailbox or climbing one flight of stairs.
- You feel unusually breathless, weak or pale, or you're more tired now than when you started.
- You notice heat intolerance, shaky hands, heavy sweating, anxiety, or weight coming off much faster than 0.5-1 lb a week after the first week.
- You feel lightheaded when you stand, which can mean blood pressure is running low.
- Your watch flags an irregular rhythm.
Get emergency care right away for chest pain or pressure, fainting, severe shortness of breath, or a racing heart with confusion. Don't wait on those.
When you see your doctor, bring your watch data and the date you started carnivore. Ask about a blood count, iron studies and a thyroid panel.
And if you're on any medication or have a diagnosed condition, don't adjust anything on your own while you sort this out. That's a job for you and your doctor together.
The bottom line
A slightly higher resting heart rate in the first weeks is common, and it usually comes down to fluid, sodium and adaptation. Salt properly, drink to thirst, protect your sleep and watch the weekly trend. If it settles, you're adapting. If it keeps climbing or brings company, that's your cue to call your doctor, not to push through.
Not a doctor: This article is general information, not medical advice. If you have a health condition or take medication, talk with your doctor before changing your diet.