Carnivore Diet Side Effects and How to Fix Them

Carnivore diet side effects at a glance

Keto flu on carnivore (“carnivore flu”)

When you stop eating carbs, insulin falls and your kidneys let go of more sodium and water. At the same time your body is shifting from burning sugar to burning fat and making ketones. The result is a few days of tiredness, headaches, irritability and fog. Mine hit on days 4 to 7, partly withdrawal from beer, soda and energy drinks.

Fix: salt every meal generously, add salt to your water or use an electrolyte mix with real sodium, and eat until full. Do not combine the first week with a big calorie cut.

Carnivore diet headache

Headaches in the first week are usually low sodium or dehydration, and sometimes caffeine or sugar withdrawal. A glass of water with a quarter teaspoon of salt, or an electrolyte drink, often helps within 30 to 60 minutes.

If headaches continue past two weeks, check your salt, food intake and coffee. A sudden, severe headache, or one with vision changes, confusion or weakness, needs medical care.

Carnivore diet diarrhea

Diarrhea is common in the first few weeks, usually because your body is not yet used to digesting large amounts of fat. Common triggers:

• Large amounts of rendered fat, butter or tallow added to meals
• Dairy, especially cream and milk
• Magnesium citrate or oxide supplements
• Sugar alcohols in “carnivore-friendly” snacks

Fix: for a week, eat leaner cuts like sirloin or 90/10 ground beef and skip added fat and dairy, then add fat back gradually. Drink extra fluids and salt. See a doctor if it is severe, bloody, comes with a fever, or lasts more than a few days.

Carnivore diet constipation

Meat is digested almost completely, so you make less stool and go less often. In week 2 I went every two to three days and took magnesium citrate once. It was not needed. Real constipation means hard, dry stools or straining, and usually points to too little fluid, salt or fat.

Fix: drink more water, salt your food, choose fattier cuts like 80/20 ground beef and ribeye, and give it a week or two. Magnesium citrate is a common short-term fix. Ongoing pain, bloating or no bowel movement for many days needs a doctor.

Carnivore diet leg cramps

Cramps, especially at night, usually mean low electrolytes. Low-carb diets increase sodium loss, and magnesium and potassium often go with it.

Fix: salt food well, take an electrolyte drink during the day, and try magnesium glycinate in the evening. It is gentler on the stomach than citrate, and it helps my sleep. The products I use are on my carnivore supplements page. Be careful with potassium supplements if you have kidney disease or take blood pressure medication; ask your doctor first.

Fatigue, brain fog and the plateau

Low energy in week 1 is adaptation. Low energy in week 6 is usually under-eating, because appetite drops and it is easy to fall to 800 or 1,000 calories without noticing.

It happened to me twice. On 400 to 1,000 calories a day I got exhausted and foggy, had trouble with my peripheral vision, and the scale stopped moving. Adding back bacon and fatty cuts cleared the fog within about a day. More food, a stronger electrolyte mix and home cooking also broke a six-week slowdown, as I describe in my carnivore diet results.

Fix: set a floor (mine is 1,600 to 1,800 calories), choose fatty cuts, and eat two real meals even on low-appetite days. The 7-day carnivore meal plan gives a sense of portions.

Carnivore diet cholesterol

You will not feel this one. LDL cholesterol often goes up on carnivore, sometimes sharply, and the rise tends to be largest in lean, active people, sometimes called “lean mass hyper-responders.” HDL usually goes up and triglycerides usually go down.

In the 2021 survey of 2,029 adults on a carnivore diet (Lennerz et al., Current Developments in Nutrition), average LDL was high, while HDL and triglycerides looked favorable. Whether high LDL carries the same risk in this context is debated, and there is no long-term outcome data.

What to do: get a lipid panel before you start and again around three months in. If LDL rises a lot, review it with a doctor. Options include eating more fish, using less butter and added fat, or moving to a less strict approach like keto.

Other side effects

• Bad breath: acetone, a ketone, can be exhaled. It usually fades after a few weeks. Water helps.
• Heart palpitations: often low electrolytes or dehydration early on. Anything persistent, or with chest pain or fainting, needs a doctor right away.
• Trouble sleeping: common in week 1. Eating earlier, cutting afternoon coffee and evening magnesium can help.
• Gout flares: uric acid can rise in the first weeks of a very low-carb diet. If you have had gout, talk to your doctor first.
• Water weight swings: dairy, condiments, restaurant meals and alcohol each added 2 to 4.6 lbs overnight for me. It is water and it comes off.

Medications, warning signs and when to see a doctor

Get medical care promptly if you have:

• Chest pain, fainting, or a racing heart that does not settle
• Diarrhea that is bloody, severe or lasts more than a few days
• Signs of dehydration: very dark urine, dizziness on standing, confusion
• Vomiting, deep rapid breathing or unusual drowsiness, especially if you have diabetes
• Vision changes or a sudden severe headache