Last updated: 15 October 2026

Your diet cannot change your body's pH, and there is no good evidence that an alkaline diet helps you fall pregnant. The vagina is meant to be acidic, but around ovulation your body makes clear, slippery mucus that helps sperm swim through, so timing sex well matters far more than pH.

What is pH?

pH is a scale that shows how acidic or alkaline something is. It runs from 0 to 14, where 7 is neutral, below 7 is acidic and above 7 is alkaline.

Different parts of your body have different pH levels on purpose. Your stomach is very acidic to break down food, while your blood stays just a little alkaline.

Can food change your body's pH?

No. Your lungs, kidneys and bones work together to keep your blood pH in a very narrow range, no matter what you eat.

The American Institute for Cancer Research says an alkaline diet cannot change body pH. So eating "alkaline foods" will not change the pH of your blood, your cervix or your vagina.

Is it bad that the vagina is acidic?

No, it is healthy. A healthy vagina has good bacteria called lactobacilli, which make lactic acid and keep the vagina acidic.

Jean Hailes explains that this acidity helps protect against infections such as bacterial vaginosis (BV). Trying to make the vagina less acidic could upset this natural balance.

How do sperm survive in an acidic vagina?

Your body has this covered. Semen is naturally a little alkaline, with a normal pH usually given as about 7.2 to 8.0.

Around ovulation, the cervix also makes a special mucus. Your Fertility says this mucus becomes clear, slick and slippery, a bit like raw egg white, and sperm can move through it more easily.

So the change that helps sperm happens on its own each cycle. It does not depend on your diet.

When is the best time to have sex to fall pregnant?

Timing matters much more than pH. The fertile window is the day you ovulate (release an egg) and the five days before it.

Your most fertile days are the three days leading up to and including ovulation. This is because sperm can live for about five days, but an egg can only be fertilised for about one day.

Signs that you are about to ovulate

• Clear, slippery mucus. Just before ovulation, your mucus becomes clear and slippery.
• Thicker mucus after. After ovulation, mucus becomes thicker and white or yellow.

If your cycles are irregular or you are not sure when you ovulate, having sex every two to three days covers all your fertile days. This takes the guesswork out of timing.

Do lubricants stop you getting pregnant?

Probably not. A 2018 study of more than 6,400 women trying for a baby found that using lubricant did not lower their chance of falling pregnant.

This was one large study that followed women over time, so it is good but not final proof. If you are worried about a product, ask your GP or pharmacist.

Do pH test strips show if your body is too acidic?

No. The pH of your urine only shows what your body is getting rid of, not the pH inside your body.

So a urine strip cannot tell you if you are "too acidic" or if an alkaline diet is working. If you are having trouble falling pregnant, see your doctor rather than relying on home pH tests.

Does healthy eating still help fertility?

Yes, just not because of pH. Healthy eating and regular exercise help you reach a healthy weight, which improves your chance of falling pregnant and having a healthy baby.

For men, eating well and staying active can improve sperm quality. Many "alkaline" tips, like eating more vegetables and drinking water, are good advice anyway.

Alcohol and caffeine

If you are planning a pregnancy, not drinking alcohol is the safest choice. Too much caffeine can also affect fertility, and pregnant women should have no more than 200 mg a day in total.

Which supplements should you take before pregnancy?

Women planning a pregnancy are advised to take folic acid and iodine. Most people are told to take 400 micrograms (mcg) of folic acid and 150 mcg of iodine each day.

Folic acid helps lower the risk of neural tube defects, which are problems with how the baby's brain and spine form. Iodine helps the body make thyroid hormones.

Many pregnancy multivitamins contain both. You can compare options in our pregnancy vitamins range, including the Elevit range.

Look for an AUST L, AUST L(A) or AUST R number on the label. The TGA says only medicines with one of these numbers are approved for sale in Australia.

For a full list of steps, read our preconception care checklist for couples. It covers health checks, vaccines, weight and more.

When should you see a doctor?

If you are under 35, see your doctor after 12 months of trying. If you are over 35, see your doctor after 6 months of trying.

See your doctor straight away if you think there may be a problem. About 1 in 6 Australian couples have trouble falling pregnant, so you are not alone.

Keep reading about fertility

To get ready as a couple, start with our preconception care checklist. Then read our guide on how men and women can boost their fertility when trying for a baby.

Dads-to-be can also read about supporting men's fertility naturally.