Electrolytes in Pregnancy: Are They Safe, and When to Call the Midwife

No trial has tested everyday electrolyte drinks, sachets or tablets in a healthy pregnancy or while breastfeeding, so this page gives what the NHS says: you may need more fluid than usual, keep caffeine to no more than 200 mg a day, and if you are being sick often and cannot keep food down, tell your midwife or doctor. Part of the Wellgard electrolyte guide.

Evidence at a glance

• Trials: two randomised trials of a medicinal rehydration solution as treatment in pregnancy (124 and 60 women) and one quasi-randomised study of extra fluids while breastfeeding (210 women).
• Largest trial: 124 women admitted with severe pregnancy sickness, given a rehydration solution by mouth or a drip for the first 12 hours.
• Strongest measured outcome: by discharge, 31 of the 61 women started on the oral solution had needed a drip.
• Not tested: any electrolyte drink, sachet or tablet in a healthy pregnancy or while breastfeeding.

Sources checked on 13 October 2026.

Are electrolyte drinks safe in pregnancy?

No trial has asked that question of an everyday electrolyte drink, sachet or tablet, so nobody can give a trial-based yes or no. Their minerals are the ones in food; what matters is how much a serving adds to your day and what else is in it.

Two randomised trials have given pregnant women a medicinal oral rehydration solution, both as treatment for a complication. In 124 women admitted with hyperemesis gravidarum, the severe form of pregnancy sickness, those drinking the solution for the first 12 hours vomited more often than those on a drip (2.6 against 1.1 episodes), and half had needed a drip by discharge.¹ The second, in 60 women with low amniotic fluid, is in the questions below.² Neither tells you anything about a sachet at home in a healthy pregnancy. If you would like to use one, show the label to your midwife or a pharmacist (see who should check first).

What does the NHS say about fluids when you are pregnant or breastfeeding?

The NHS suggests 6 to 8 cups or glasses of fluid a day for most people and says you may need more if you are pregnant or breastfeeding; it gives no separate pregnancy figure. The everyday check is your pee, which the NHS says should be "a clear pale yellow colour".³

Water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count. The pregnancy limit is caffeine: "do not have more than 200mg of caffeine a day if you're pregnant", which the NHS links to a higher risk of miscarriage or low birth weight.³ It puts a cup of instant coffee at about 100 mg and a cup of tea at about 75 mg, and lists guarana and "some health or fitness supplements" as sources.⁴

Pregnancy sickness and dehydration: when should you call the midwife?

If you are "being sick frequently and cannot keep food down", the NHS says tell your midwife or doctor, or contact the hospital as soon as possible, because of the risk of dehydration.⁵ An electrolyte sachet is not a treatment for pregnancy sickness.

Around 8 in 10 pregnant women feel sick, are sick or both, and hyperemesis gravidarum affects around 1 to 3 in 100.⁵ The NHS lists the signs of dehydration as feeling thirsty, tired, dizzy or lightheaded, not peeing very much, and dark yellow, strong-smelling pee.⁵ Call your midwife, GP or 111 if you are vomiting and have very dark pee or have not had a pee in more than 8 hours, cannot keep food or fluids down for 24 hours, or feel very weak, dizzy or faint when standing up; otherwise, drink plenty of fluids such as water, sipping little and often.⁶

When sickness is severe, electrolytes become a hospital job: the UK obstetric guideline recommends a salt-water drip with added potassium, guided by daily blood tests of electrolyte levels.⁷ A pharmacy rehydration medicine and an electrolyte drink are compared in rehydration sachets when you are ill; in pregnancy, ask the pharmacist or your midwife before using either.

What should you read on an electrolyte label if you are pregnant or breastfeeding?

Four things, each with an NHS line to check against; take anything unclear to your midwife or a pharmacist.

• Sodium. The NHS limit is 6 g of salt a day, which is 2.4 g of sodium; multiply a label's sodium by 2.5 to get salt.⁸ The European Food Safety Authority's safe and adequate intake, 2.0 g of sodium a day, applies in pregnancy and breastfeeding as for other adults.⁹ In 506 athletes, sweat carried about 0.8 g of sodium a litre at about 1.2 litres an hour;¹⁰ on a day without heavy sweating, a serving's sodium simply counts towards your 6 g (see how much salt a day).
• Caffeine. Some drink mixes add caffeine or guarana; count it towards the 200 mg.⁴
• Herbs and botanicals. The NHS limits herbal tea to 4 cups a day in pregnancy, says avoid teas containing liquorice root, and notes "There's not much research on the effects of drinking herbal teas in pregnancy".⁴ An added herb in a drink is a question for your midwife or pharmacist.
• Vitamin A. "Do not take cod liver oil or supplements containing vitamin A (sometimes called retinol)" in pregnancy, says the NHS: "Always check the label".¹¹

Sodium has no authorised health claim in Great Britain, so a label's sodium figure is there to be counted.¹²

Does breastfeeding change your electrolyte needs?

Not in any figure the NHS gives. It says you may need more fluid while breastfeeding and suggests a drink beside you when you settle down to feed, with water, low fat milk or diluted pure fruit juice as good choices.^{3, 13} No trial has tested electrolyte drinks while breastfeeding.

Extra fluid has not been shown to raise milk supply. A Cochrane review found no randomised trial; its one quasi-randomised study, of 210 women in the 1950s and at high risk of bias, reported that advice to drink extra fluids did not improve milk production.¹⁴ Caffeine "can reach your baby through your breast milk", says the NHS, which recommends no more than 200 mg a day while breastfeeding and cutting down, especially while your baby is under 6 months.¹³

What we don't know

• No trial has tested an electrolyte drink, sachet or tablet in a healthy pregnancy or while breastfeeding.
• The low-amniotic-fluid trial cited here was small, single-centre and outside the UK.
• No study has measured milk supply against extra fluid or electrolytes with modern methods; the one study weighed babies before and after feeds.

Frequently asked questions

What is the best electrolyte for pregnancy?

No trial has compared one with another in pregnancy, so none can be ranked best. Use the checklist above: sodium against the 6 g day, caffeine against 200 mg, no vitamin A, and any herb cleared with your midwife or pharmacist. The wider guide is how to read an electrolyte label.

Can electrolytes help with pregnancy cramps or swelling?

No trial has tested an electrolyte drink for either. For cramp the NHS suggests ankle and leg exercises and pulling your toes hard up towards your ankle.¹⁵ Magnesium alone has been trialled for pregnancy leg cramps, with inconsistent results (four trials, 332 women, pooled in 2021);¹⁶ ask your midwife first. Sudden swelling of the face, hands or feet, a severe headache that does not go away with simple painkillers, or blurred vision or flashing lights can be signs of pre-eclampsia: the NHS says get urgent medical help, calling your maternity unit, or 111 if you cannot.¹⁷

Can I drink an electrolyte drink while breastfeeding?

No trial has tested it. The NHS advice is plenty of fluids, with a drink beside you as you feed.¹³ If you use a drink mix, count any caffeine towards the 200 mg and ask a pharmacist about added botanicals.

Is milk or coconut water a better choice in pregnancy?

Both are foods carrying sodium and potassium, and neither has been compared in pregnancy. In a trial of 13 drinks in 72 men, funded by a hydration research institute whose advisory board the lead author chaired, full-fat milk, skimmed milk and a rehydration solution were kept in the body longer than water over four hours; coconut water was not tested.¹⁸ In pregnancy the NHS says avoid unpasteurised milk.⁴ Amounts per glass are in which drinks contain electrolytes.

Can drinking more fluid raise low amniotic fluid?

Low amniotic fluid is found on a scan and managed by your maternity team. In a trial of 60 women at term in India, after three days of 2 litres a day of a rehydration solution, 15 of 30 had an amniotic fluid index of 7 to 8 cm against 6 of 30 on usual intake (16 and 15 at the start; P = 0.026); the authors declared no funding.² It did not test a home sachet; ask your midwife.

Sources

1. Wan Jabarudin WNE et al. International Journal of Gynecology and Obstetrics 2024. Randomised trial, 124 women in hospital with hyperemesis gravidarum, 12 hours. PubMed 38358264
2. Hadalageri AS et al. Cureus 2025. Randomised trial, 60 women at term with low amniotic fluid, 3 days; index counts from the full text; no funding declared. PubMed 40352048
3. NHS. Water, drinks and hydration. Page last reviewed 17 May 2023 (review overdue); checked 13 October 2026. nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/water-drinks-nutrition
4. NHS. Foods to avoid in pregnancy. Page last reviewed 15 June 2026. nhs.uk/pregnancy/keeping-well/foods-to-avoid
5. NHS. Severe vomiting in pregnancy. Page last reviewed 11 January 2023 (review overdue); checked 13 October 2026. nhs.uk/pregnancy/complications/severe-vomiting
6. NHS. Vomiting and morning sickness. Page last reviewed 17 April 2024. nhs.uk/pregnancy/common-symptoms/vomiting-and-morning-sickness
7. Nelson-Piercy C et al. (RCOG Green-top Guideline No. 69). BJOG 2024. Clinical guideline. PubMed 38311315
8. NHS. Vitamins and minerals: others. Page last reviewed 3 August 2020 (review overdue); checked 13 October 2026. nhs.uk/conditions/vitamins-and-minerals/others
9. EFSA NDA Panel. EFSA Journal 2019. Scientific opinion, sodium reference values. PubMed 32626425
10. Baker LB et al. Journal of Sports Sciences 2016. Observational, 506 athletes; authors at a sports-drink maker's research institute. PubMed 26070030
11. NHS. Pregnancy vitamins and supplements. Page last reviewed 3 June 2026. nhs.uk/pregnancy/keeping-well/pregnancy-vitamins-and-supplements
12. Department of Health and Social Care. GB nutrition and health claims register. Last updated 19 May 2026. gov.uk
13. NHS. Breastfeeding and diet. Page last reviewed 15 May 2026. nhs.uk/baby/breastfeeding-and-bottle-feeding/breastfeeding-and-lifestyle/diet
14. Ndikom CM et al. Cochrane Database of Systematic Reviews 2014. Systematic review, one quasi-randomised study, 210 women. PubMed 24916640
15. NHS. Common health problems in pregnancy. Page last reviewed 22 April 2024. nhs.uk/pregnancy/common-symptoms/common-health-problems
16. Liu J et al. Taiwanese Journal of Obstetrics and Gynecology 2021. Pooled analysis of 4 randomised trials, 332 pregnant women. PubMed 34247796
17. NHS. Pre-eclampsia. Page last reviewed 23 March 2026. nhs.uk/conditions/pre-eclampsia
18. Maughan RJ et al. American Journal of Clinical Nutrition 2016. Randomised trial, 72 men, 13 drinks, 4 hours; funded by a hydration research institute whose advisory board the lead author chaired. PubMed 26702122

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