Medicines can help with weight loss, but they work best alongside changes to eating and activity, not instead of them. Here’s how the main options compare. Only one is available without a prescription.

Over the counter: orlistat 60 mg (Alli)

• How it works: it blocks about a quarter of the fat you eat from being absorbed.
• Who it’s for: adults aged 18 and over with a BMI of 25 or more, together with a reduced-calorie, low-fat diet.
• How to take it: one capsule with each main meal that contains fat, up to three times a day.
• Side effects: oily spotting, wind with an oily discharge, and urgent bowel movements, especially after high-fat meals. Keeping to about 15 g of fat per meal reduces them.
• Important: take a multivitamin containing vitamins A, D, E and K at bedtime. Don’t use orlistat if you take ciclosporin, and ask a pharmacist if you take levothyroxine, warfarin or epilepsy medicine.
• Results: modest, typically a few extra pounds over a year compared with diet alone.

Prescription medicines

Doctors may prescribe a weight-loss medicine to adults with a BMI of 30 or more, or 27 or more with a weight-related condition such as type 2 diabetes, high blood pressure or sleep apnoea.

• Semaglutide (Wegovy) and tirzepatide (Zepbound): weekly injections that reduce appetite and slow stomach emptying. In trials, average weight loss was about 15% with semaglutide and around 20% with tirzepatide at the highest dose. The same medicines are sold for diabetes as Ozempic and Mounjaro. See Ozempic vs Mounjaro.
• Liraglutide (Saxenda): a daily injection from the same family, with smaller average weight loss.
• Phentermine-topiramate (Qsymia) and naltrexone-bupropion (Contrave): tablets that reduce appetite.

Common side effects of the injections include nausea, vomiting, diarrhoea and constipation, mostly when starting or increasing the dose. Rarer but serious risks include pancreatitis and gallbladder problems. They aren’t used in people with a personal or family history of medullary thyroid cancer or MEN2 syndrome, or in pregnancy.

Weight often returns after stopping, so these medicines are usually long-term treatments.

Avoid fake and unapproved products

The FDA has warned about counterfeit semaglutide and about unapproved “weight loss” products sold online, some containing the wrong dose or hidden drugs. Prescription weight-loss medicines should come from a licensed pharmacy with a valid prescription from a doctor who has assessed you. Be wary of any website that offers them without one.

What about supplements?

No supplement has good evidence for meaningful weight loss. Products sold for weight loss have been found to contain hidden prescription drugs, including some withdrawn for heart risks.

Start with the basics in how to lose weight safely.

Related guide: Berberine for weight loss: does “nature’s Ozempic” work?

More in our Weight Management guide: all our articles on this topic in one place.

This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist. Always read the label before using any medicine.

There is no single best diet for weight loss. Studies comparing popular diets find that the one you can stick to matters more than the type. What works is a set of habits that reduce how much energy you take in, kept up over months.

Aim for a realistic pace

US health guidance suggests aiming for about 1 to 2 pounds (0.5 to 1 kg) a week. People who lose weight at this pace are more likely to keep it off. Losing just 5 to 10% of your body weight can lower blood pressure, improve blood sugar and reduce joint pain.

Habits that make the biggest difference

• Cut sugary drinks and limit alcohol. Soda, sweet coffee drinks, juice and alcohol add a lot of calories without filling you up.
• Include protein at every meal, such as eggs, yogurt, beans, fish, chicken or tofu. It helps you feel full and protects muscle while you lose weight.
• Fill half your plate with vegetables and choose whole grains. Fibre adds volume with few calories.
• Watch portions of energy-dense foods such as fried food, pastries, cheese and nuts. A smaller plate helps.
• Cook more and eat out less. Restaurant meals are usually much larger than home portions.
• Track what you eat, at least for a few weeks. People who keep a food log tend to lose more weight.

Move more

• Aim for at least 150 minutes a week of moderate activity such as brisk walking.
• Add strength exercises on 2 days a week to keep muscle.
• Everyday movement counts too: take the stairs, walk while on calls, park further away.

Exercise alone usually leads to modest weight loss, but it’s one of the best predictors of keeping weight off.

Sleep and stress

Short sleep increases hunger hormones and cravings. Aim for 7 or more hours a night. Stress can drive comfort eating, so find other ways to unwind, such as a walk, calling a friend or a hobby.

What to avoid

• Very low calorie diets (under about 800 calories a day) unless supervised by a doctor.
• Skipping meals and then overeating later.
• Weight-loss supplements with big promises. The FDA has found hidden prescription drugs in many of them.

When to see a doctor

See a doctor if you’ve gained or lost weight without trying, if you have a condition such as diabetes or heart disease, or if you’ve tried hard and still can’t lose weight. Medical causes such as an underactive thyroid can be checked, and some people qualify for weight-loss medicine. If thoughts about food or weight are causing you distress, talk to a doctor about that too.

Stuck after a good start? Read why weight-loss plateaus happen and how to get past them.

Related guide: Ayurvedic herbs for weight loss: what the evidence says

More in our Weight Management guide: all our articles on this topic in one place.

This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist. Always read the label before using any medicine.

Head lice are common in school-age children and have nothing to do with how clean someone is. They spread through head-to-head contact. They’re a nuisance but don’t carry disease, and most cases clear with one over-the-counter treatment plus combing.

How to check for head lice

• Look for live lice: small greyish-brown insects about the size of a sesame seed, moving close to the scalp.
• Look for nits (eggs) firmly stuck to hairs within about 6 mm (¼ inch) of the scalp, especially behind the ears and at the nape of the neck. Unlike dandruff, they don’t brush off easily.
• The most reliable way to check is wet combing: wet, conditioned hair combed section by section with a fine-toothed lice comb.

Only treat if you find a live louse. Nits alone may be old, empty shells.

Over-the-counter treatments compared

• Ivermectin 0.5% lotion (Sklice): applied to dry hair for 10 minutes, then rinsed. Usually one application is enough and nit-combing isn’t required. For ages 6 months and over.
• Permethrin 1% (Nix): applied to freshly washed, towel-dried hair without conditioner for 10 minutes, then rinsed. Repeat on day 9. For ages 2 months and over.
• Pyrethrins with piperonyl butoxide (Rid): applied to dry hair for 10 minutes, then repeated 7–10 days later. For ages 2 and over. Avoid if you’re allergic to ragweed or chrysanthemums.

In many parts of the US, lice have become resistant to permethrin and pyrethrins. If one of these hasn’t worked after two correct treatments, try a different type rather than repeating it.

Tips for treatment that works

• Follow the label exactly. Use enough to soak all the hair and the scalp.
• Don’t use conditioner or a combined shampoo-conditioner before permethrin, because it coats the hair.
• Comb with a lice comb every 2–3 days for 2 weeks to catch any lice that hatch.
• Check everyone in the household, but only treat those with live lice.
• Never use flammable products such as kerosene or petrol on the hair.

Cleaning at home

Lice die within 1–2 days off the scalp, so a big clean-up isn’t needed. Wash pillowcases, hats and towels used in the last 2 days in hot water (at least 130°F / 54°C) and dry on high heat, or seal items in a plastic bag for 2 weeks. Soak combs and brushes in hot water. Insecticide sprays for the home aren’t needed.

Can my child go to school?

The American Academy of Pediatrics advises that children don’t need to miss school because of head lice. They can go back after the first treatment.

See a doctor if

Lice keep coming back after two different treatments, the scalp looks infected (crusting, oozing, swollen glands), or the child is under 2 months old. Prescription options include spinosad and malathion.

Read more about ivermectin and its uses.

Related guide: Permethrin 1% for head lice: how to use it and what to do if it fails

More in our Lice and Parasites guide: all our articles on this topic in one place.

This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist. Always read the label before using any medicine.

Ivermectin tablets are usually taken as a single dose and most people tolerate them well. This guide covers the side effects to expect, the ones that need a doctor, and the warning signs of taking too much.

Common side effects of ivermectin tablets

• dizziness
• nausea, diarrhoea or stomach pain
• tiredness or lack of energy
• itching or a mild rash

These are usually mild and pass within a day or two.

Reactions to dying parasites

When ivermectin is used for river blindness (onchocerciasis), the body can react to the parasites as they die. This is called the Mazzotti reaction. It can cause itching, fever, swollen glands, joint pain and, less often, a drop in blood pressure that makes you dizzy when you stand up. Lie down if you feel faint and tell your doctor.

Serious side effects: get medical help

• a severe skin rash with blistering or peeling
• yellowing of the skin or eyes, or dark urine
• confusion, extreme sleepiness or difficulty walking
• seizures
• swelling of the face, lips or throat, or difficulty breathing

Overdose warning signs

Most ivermectin overdoses in the US have involved animal products or taking more than prescribed. Signs include:

• nausea, vomiting and diarrhoea
• confusion, drowsiness or hallucinations
• unsteady walking, tremor
• blurred vision
• low blood pressure, seizures or coma

If you think someone has taken too much, call Poison Control on 1-800-222-1222, or 911 if they are very drowsy, having a seizure or struggling to breathe.

Medicines that interact with ivermectin

• Warfarin: there are reports of a raised INR (increased bleeding risk), so your INR may need checking.
• Sedatives such as benzodiazepines or barbiturates: tell your doctor if you take these.
• Some medicines that change how the liver breaks down drugs, including certain HIV medicines, antifungals and ciclosporin. Your pharmacist can check your list.

Side effects of ivermectin lotion and cream

The lotion used for head lice and the cream used for rosacea are applied to the skin, so very little reaches the bloodstream. Possible effects include eye irritation, redness, burning, dry skin or dandruff. Keep them away from the eyes.

See also: what ivermectin is used for, and what it doesn’t treat.

More in our Lice and Parasites guide: all our articles on this topic in one place.

This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist. Always read the label before using any medicine.

Ivermectin is an antiparasitic medicine. It has been used for decades to treat certain worm infections, and it has saved millions of people from river blindness. It also became one of the most searched medicines during the COVID-19 pandemic. This guide explains what ivermectin does and doesn’t do, based on the evidence.

What ivermectin is approved to treat

In the US, ivermectin comes in three forms, each for different conditions:

• Tablets (prescription): approved for strongyloidiasis (a threadworm infection of the intestine) and onchocerciasis (river blindness). Doctors also prescribe them for some other parasitic infections, including scabies, particularly severe (crusted) scabies.
• 0.5% lotion (Sklice, over the counter): for head lice in adults and children aged 6 months and over. See our guide to head lice treatment.
• 1% cream (Soolantra, prescription): for the bumps and spots of rosacea.

How ivermectin tablets are taken

• A doctor works out the dose from your body weight. It is often a single dose, sometimes repeated.
• Tablets are taken on an empty stomach with water.
• Depending on the infection, you may need follow-up stool tests to check the treatment worked.

Because the right dose and the need for a repeat dose depend on the infection and on your weight, ivermectin tablets need a prescription and a diagnosis.

What about COVID-19?

Several large randomised trials, including ACTIV-6, TOGETHER and PRINCIPLE, tested ivermectin in people with COVID-19. They found it did not speed up recovery or reduce hospital admissions compared with a placebo. The FDA has not authorised or approved ivermectin to prevent or treat COVID-19.

Never use animal ivermectin

Ivermectin products for horses, cattle and dogs are much more concentrated and are made for animals that weigh far more than a person. US poison centres have reported people needing hospital treatment after taking them, with confusion, seizures, very low blood pressure and coma. Never take a veterinary product.

Check with a doctor first if you

• are pregnant or breastfeeding
• have liver disease
• take warfarin or other regular medicines
• have lived in or travelled to Central or West Africa. Ivermectin can cause serious reactions in people with a heavy Loa loa (eye worm) infection, so doctors test for it first.
• want to treat a child who weighs less than 15 kg (33 lb)

Side effects

Most people have no side effects or mild ones such as dizziness, nausea or itching. Read our full guide to ivermectin side effects, interactions and overdose warning signs.

More in our Lice and Parasites guide: all our articles on this topic in one place.

This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist. Always read the label before using any medicine.