To start keto, first check with your doctor if you have a health condition or take medicines, especially for diabetes or blood pressure. Then set a daily limit of about 20 to 50 g of net carbs, build meals around protein, non-starchy vegetables and healthy fats, and clear out or move aside the high-carb foods you’ll be tempted by. Plan your first week of meals, drink plenty of water, add a little salt to food to ease keto flu, and expect to feel tired or foggy for a few days. After two or three months, review how it’s going: weight, energy, blood tests and whether it’s sustainable. Many people do best moving to a more flexible low-carb diet after the first phase, as Harvard’s Nutrition Source notes keto is hard to follow long term.
Step 1: Check whether keto suits you
Keto isn’t right for everyone. Talk to your doctor before starting if you:
- Take insulin or other diabetes medicines, which may need reducing to avoid low blood sugar. The NHS explains the symptoms of hypoglycemia.
- Take SGLT2 inhibitors, which carry a risk of ketoacidosis on very low-carb diets.
- Take blood pressure medicines or diuretics.
- Have kidney, liver, pancreas or gallbladder disease.
- Are pregnant, breastfeeding or trying to conceive.
- Have a history of eating disorders.
- Are under 18.
Our guide to whether keto is safe long term covers the risks.
Step 2: Understand the basics
A ketogenic diet keeps carbohydrate low enough that the body switches to using fat and ketones as its main fuel. A typical starting point:
| Macronutrient | Typical target |
|---|---|
| Net carbs | 20 to 50 g a day |
| Protein | About 1.2 to 1.6 g per kg of body weight, or a palm-sized portion at each meal |
| Fat | The rest of your energy, mainly from unsaturated sources |
Net carbs are total carbs minus fiber. Our guides to calculating net carbs and keto macros explain the numbers.
Step 3: Stock your kitchen
- Proteins: eggs, chicken, fish, seafood, beef, pork, tofu, cheese.
- Vegetables: leafy greens, broccoli, cauliflower, zucchini, peppers, mushrooms, cabbage, asparagus, green beans.
- Fats: extra virgin olive oil, avocado, nuts, seeds, butter in moderation.
- Dairy: hard cheeses, plain Greek yogurt, cream.
- Fruit: berries in small portions.
- Flavor: herbs, spices, garlic, lemon, mustard, vinegar.
Move bread, pasta, rice, cereal, sweets and sugary drinks out of easy reach, or out of the house. Our keto diet food list has a complete checklist, and our guide to keto cooking basics covers the skills you’ll use.
Step 4: Plan your first week
| Day | Breakfast | Lunch | Dinner |
|---|---|---|---|
| 1 | Scrambled eggs with spinach | Chicken salad with avocado and olive oil | Salmon with roasted broccoli |
| 2 | Greek yogurt with raspberries and walnuts | Leftover salmon salad | Beef stir-fry with cauliflower rice |
| 3 | Omelet with cheese and peppers | Tuna-stuffed avocado and cucumber | Chicken thighs with green beans and garlic butter |
| 4 | Chia pudding with almond milk | Egg muffins and salad | Garlic shrimp with zucchini noodles |
| 5 | Eggs with smoked salmon | Leftover chicken and slaw | Burger without the bun, with salad |
| 6 | Greek yogurt and berries | Cheese, olives, meats and vegetables | Creamy Tuscan salmon with spinach |
| 7 | Bacon or mushrooms with eggs | Leftovers | Roast chicken with cauliflower mash |
Our keto meal plan has more detail, and recipes such as our garlic shrimp with zucchini noodles and creamy Tuscan salmon fit the plan.
Step 5: Prepare for keto flu
In the first week or two, many people feel tired, headachy, irritable or dizzy as the body adapts and loses water and salt. To ease it:
- Drink plenty of water.
- Add salt to meals, or have a cup of broth, unless you’ve been told to limit salt.
- Eat potassium- and magnesium-rich foods such as avocado, spinach, nuts and seeds.
- Ease off intense exercise for the first week.
- Sleep well.
Our guides to keto flu and electrolytes have more.
Step 6: Track and adjust
- Track carbs for the first few weeks with an app or food diary. Hidden carbs in sauces, dressings and drinks add up quickly.
- Don’t over-restrict. Eat enough protein and vegetables, and don’t combine keto with a very large calorie deficit.
- Measure progress with how your clothes fit, your waist, energy and blood sugar, not just the scales. Early weight loss is largely water.
- Testing ketones is optional. Many people never test.
Step 7: Review after 2 to 3 months
Ask your doctor for blood tests, including cholesterol, kidney function and blood sugar, and think honestly about how keto fits your life. Many people stay strict for a few months, then move to a more flexible lower-carb or Mediterranean-style diet to maintain their results. Our comparison of keto vs low carb vs Atkins explains the options.
Warning signs to stop and get help
Seek medical help if you have nausea, vomiting, stomach pain, fast breathing, confusion or unusual drowsiness, especially if you have diabetes, as these can be signs of ketoacidosis, which the NHS explains. Also see your doctor for persistent dizziness, palpitations or fainting.
Common questions
How long does it take to get into ketosis?
Usually 2 to 4 days of eating under about 20 to 50 g of net carbs. Our guide to how long it takes to get into ketosis explains more.
How much weight will I lose in the first week?
Often 1 to 3 kg, mostly water. After that, weight loss usually slows to a steadier pace.
Do I need supplements on keto?
Most people don’t, if they eat plenty of vegetables. Vitamin D in winter is advised for everyone in the UK. Our guide to keto supplements covers the rest.
Safety note: Keto isn’t suitable for everyone. If you have diabetes, kidney or liver disease, take regular medication, or are pregnant or breastfeeding, talk to your doctor before cutting carbs this far (why it matters).
This article is general information, not medical advice. Talk to your doctor or a registered dietitian before making big changes to how you eat, especially if you have a health condition, take regular medication, or are pregnant or breastfeeding.
